THERE HAVE always been Meridian Hill freaks who maintain that no garden, no park, here or elsewhere, in this world or the next, is so handsome.

They err, of course, yet it is a fact this 12-acre walled oasis a mile north of the White House deserves the rank of a national living and concrete treasure and merits far more than a few terse words on Sunday morning.

It is, to begin with, designed in the Italian Renaissance style with a rectangular upper terrace 900 feet long, connected by a water staircase or cascade to a huge formal fountain-studded pool on the lower terrace.

Most American city parks are ornamental wildernesses, like Rock Creek or Great Falls.

The romantic euphoria of 19th-century park planners, and their 18th-century English predecessors, evidently required squiggly roads and trails to set off the poison ivy and other natural wonderments, and such parks are greatly admired by those who ride through them in taxi cabs.

But Meridian Hill is built, by contrast, on sound lines, with tree-lined promenades, enormous vases, utterly sound masonry work, and enough benches to seat the Eastern Seaboard. It was meant for people to walk an sit in.

It is a treasure among parks, and probably there is no other in America that - but then it is easy to become a Meridian Hill freak. A bit of history may calm us:

The land was owned by the Peter family who sold it to Washington Bowie who sold it (about 110 acres) in 1816 for $13,000 to Commodore David Porter.

Commodore Porter, who had a good bit of prize money for his naval exploits, resolved to spend his sunset as a farmer and, having built a handsome dwelling, imported bulls from England and did such other good things as a gentleman farmer ought to do. An intimate of the commodore's observed:

"All sailors imagine themselves competent to manage a farm and are never satisfied until they own one . . . The captain was so proud of his farming that he supplied his acquaintances with the best of vegetables for nothing. He had a kitchen garden of five acres and had to buy vegetables for winter; he had 10 acres in corn, oats, wheat, and was obliged to purchase grain . . ."

It must have been a great comfort, esthetically, pointing somewhat indirectly to the beauties of Meridian Hill that were to come.

The land passed hands a few times since. During the Civil War, troops from New York and Massachussets camped there, and accounts survive commending superb view down over the city and assuring worried relatives that the hospital (in the commodore's old house) was very nice indeed.

This land was subdivided in 1867 to the excitement of hardly anybody until Mary Henderson took the world in hand and finished her red sand-stone mansion, or castle as it was called, in 1836, across 16th Street from what is now Meridian Hill Park.

The name alludes to the meridian of Washington, that line that splits the lozenge of Washington north to south into two triangles.

Thomas Jefferson once hoped the Washington meridian would replace Greenwich meridian as the place where the world starts. The site of the park has been called Meridian Hill at least since Porter bought the land in 1816. It is now unofficially often called Malcolm X Park, by resolution of the D. C. government, though the Interior Department says there is not authority for a mayor to rename a national property. As far as Interior is concerned, it will always was Meridiand Hill Park and still is.

he old stone that marked the meridian was moved - the spot is near the middle of 16th Street - and some said it should have been left where it was, only buried deeper.

When President John Quincy Adams left the White House to his successor, Andrew Jackson, he did not bother with the ceremony of turning the place over in person, but simply moved out and into Meridian Hill, the Porter place.

It is not entirely clear how that happened, since Porter and Adams had been cool for years though some misunderstanding, and when Porter went with Lafayette to the White House in 1824 to see President Adams (and Lafayette was supposed to straighten out things between Adams and Porter) Mr. Adams greeted Lafayette with as much enthusiasm as an Adams can command but ignored Mr. Porter on the portico, a slight Porter is known to have been annoyed at.

Meanwhile as the decades slid by, the area of Meridian Hill was almanac of Meridian Hill lore, said land was cheap and the houses were modest - "It was many years before such conveniences as sewers, water and gas were available." For many of those residents, he went on, "this was the kind of pioneering and sacrifice" that made American great.

He digressed - he commonly did so - to observe that others stayed down in built-up Washington paying rents instead of acquiring a modest house without fancy utilities, and (Proctor speculated darkly) may well have been on the dole and plotting share-the-wealth programs so we can all "be poor together."

He felt strongly that Mrs. Henderson, presiding over that part of town from Henderson Castle after 1887, saved Meridian Hill from "the bowwows." All right-thinking people (he strongly suggested) were opposed to "small cheap rows of houses," such as those little $20,000 hovels in Georgetown that don't even have a side yard or a back garden to speak of.

Anyway, Mary Foote Henderson saved Meridian Hill from this frightful fate by buying up land across from her house. (The site of her house is now partly occupied by little row houses that are indeed small but no longer cheap.)

Mrs. Henderson married John B. Henderson, the senator who was one of 19 who voted agaisnt the impeachment of President Andrew Johnson. Mrs. Henderson was one of the great Washington hostesses, though in one of her numerous will she left her estate to the health food people at Battle Creek, later changing her mind.

She was a vegetarian and disapproved of wine, liquor, tobacco, coffee and tea in her later years. It was said (but it was not true, being the invention of a wit) that when Mrs. Henderson took her stand against alcohol, she ordered the entire wine cellar of her house (which was celebrated) poured into 16th Street and that thousands of the thirsty came from distant stages to be healed in that particular Ganges. Mrs. Henderson was the sort of person such stories are told about, without any basis of fact. (She got rid of the wine, but not in 16th Street.)

The more Mary Henderson thought about 16th Street, and her house on it, the more she concluded it might as well be the world's preeminent boulevard lined with embassies, the Vice President's Mansion, and so forth.

She built and sold or rented to several nations' embassies near her house. She decided a splendid formal garden (Meridian Hill Park) would add class to right, so she sold Congress first the idea then the land. She paid $130,000 and got $490,000 from the government for it. From her windows, then, she should be able to look across the street to a great garden built at public expense ($1 1/2 million got it in pretty good shape, though it would cost vastly more now) plus a tidy return on her investment in the land.

This was the same Mrs. Henderson who talked Congress into calling 16th Street the Avenue of the Presidents, but then they wearied and changed the named back.

Mrs. Henderson died in 1931, but by then the park was well along, and even the cascade or water staircase (adapted from Italian models) was pouring water by 1932.

The grand design called for great patches of water lillies and (though it was not part of the contract) elegant people, possibly with parasols, strolling beneath the elms and clipped horn-beams, a retreat for nannies and perambulators, though in the afternoon ladies should have showed up in silk print dresses and perhaps a fellow would bring them some lemon ice.

It has not worked out that way. The neighborhood, for all Mary Henderson's efforts, is not very grand and besides the general ideal is no longer widely held in cities. During the day the park is alive with neighborhood people - few parks can be so fully used by citizens.

On hot mornings children play in sand at the northeast corner of the park (where a Baptist school for training black ministers and teachers stood in the past century) while older children favor the lower terrace with its great ornamental pool.

This pool, by the way, and the park's fountains, use recirculated water, so visitors during a water shortage should not have fits at the thought of millions of gallons running into the Potomac.

The water is not purified to safe human standards and it is illegal to swim. The children do not swim, but they get in and splash, along with some of the most excited dogs outside a butcher shop. They lend great animation to the scene and on two visits I did not see the constabulary shipping people off to prison. It is, however, possibly dangerous to health. As what is not.

The masonry - concrete, to be blunt - is superb.

Congress refused to put up the money for stone walls, stone obelisks, stone staircases and so on, so the problem was how to make the concrete handsome enough to justify its massive use in a formal garden.

The park land was bought by the federal government in 1910, winding up with the National Park Service in 1933. In 1914 George Burnap, architect, drew several designs for development as formal garden and these were modified by Howard Peaslee, architect, and the planting plans were Vitale, Bonicheroff and Geifert, New York.

In 1912-14, $52,500 was spent on plans and early development for each of several years afterwards, $50,000 went to the park. In 1919 this fell to $25,000, but rose the next year to $30,000. From 1928-36 the annual sum rose to $92,000 and up to $145,000, but for the period 1933-35 no money was spent.

By the time the park was finished in 1936, $1.64 million had been spent, including the land, all the masonry work, the cascades, fountains and grading.

The planting is unexceptional but the concrete work is marvelous. It is said to be the first monumental use of exposed aggregate, in which small stones are exposed by scrubbing away the outer surface before it hardens, the cleaning with muriatic acid.

The principle is simple enough, but the execution requires care, and one has only to look at work done either before or after Meridian Hill to see the quality of care taken in the park.

John Early began experimenting with concrete before World War I (Meridian Hill is one of his earlier constructions) and the problem was to increase hydration of the cement so structural strength would be quickly attained.

This would permit removal of the forms (into which the concrete had been poured) while the concrete was still workable on its surface.

Early lined his forms with sheet metal, and heated the elements of the concrete, the central point being to strip the forms as soon as possible.

At first he tried for effects from alone, constrasting planes, cast balustrades (smooth cement) and heavy use of rustication, but he found the effect a bit lifeless.

His earlier exposed aggregate work showed concentrations of rock with expanses of plain concrete between, but later he became meticulous - fanatical in the best way - about the size of his pebbles, working them out precisely (smaller pebbles are used in balustrades than in retaining walls, for example) and giving great attention to color.

Early's specifications for the work (for which contracts were let) said care must be used in not having bare areas of concrete, etc., but as the magazine Landscape Architecture observed, these general specifications "might not lead to the desired results." Somebody, presumably Early, inspired the laborers to great pride in their work. Maybe he simply reminded them how good they could be.

The result is a sharpness and clarity, almost unknown in the slapdash concrete work one usually sees, throughout Meridian Hill. At first it is equally remarkable that the balusters were poured in position, and not painstakingly made individually in an arts shop for $50 each.

Modern repair work in the park (made necessary especially on the paved walks, which were ignored for years after World War II) shows the sad falling off of effect.

For the seats and balustrades plaster forms were used, heavily coated with crank-case oil, but most of the work used wooden forms lined with metal.Early simply experimented with techniques until he got it right, then explained in careful detail to foremen how to do it.

The modern trouble (as far as a gardener is concerned) is that the workmen available have not settled in, so to speak, to a perfected technique, though the work at Meridian Hill is ample testament that with sufficient time and interest, ordinary contractors can do superb jobs.

There were concerts at Meridian Hill for some years, and dramas were offered. These were discontinued, partly because money run short and partly because of increased public fear of crime in parks. From 1945 to the 1960s, very little was spent on Meridian Hill, the Interior Department points out.

This was a period of concentration on the Mall area, but there was a revival of interest in the park with the Summer in the Parks program starting in 1968.

In 1972, Meridian Hill funding rose to $112,000 and for the past two years about $200,000 a year have been spent. The result is many repairs, better lighting and replacement of trees and play areas.

There seems to have been a revival of neighborhood pride in the park - it would be expecting a good bit for a neighborhood to take pride in a park when the city neglected it shamefully, and the increased funding has evidently helped.

As for Mrs. Henderson, it is doubtless reward enough to have lobbied the park into existence and she could probably have got used to the dogs in the fountain basins (as long as they were vegetarian dogs).