One day in 1790, the Founding Fathers had a meeting. They had already decided to place the national capital astride the Potomac River. The question now was how to configure the son-of-a-gun.

Squares, trapezoids, circles - the Founding Fathers considered everything. Finally, though, they settled on our familiar diamond. They made it ten miles on a side, and tilted it up so it would point toward true north.

Why a diamond? Presumably the Fathers wanted to suggest that Washington would be forever. My own hunch is that the boys were playing bridge during their momentous meeting, and one Founding Father was trying to tell his partner which suit to lead. Whatever, we are stuck with the results.

I say stuck having just spent a day walking, talking and mostly driving around the 36 miles of the diamond that border Maryland.

The route takes one along Southern, Eastern and Western Avenues. What one comes away with, beside three fewer gallons of gas, is the strong impression that the District's border has created many more problems than it has solved.

For what the Founding Fathers did was simply to cut a diamond-shaped cookie. It was purely arbitrary. And gentlemen, it looks it.

Consider one half-mile stretch along the city's border with Capitol Heights.

Eight Washington streets and five Capitol Heights streets come to a screeching halt at the border. None of the 13 join or continue into any of the others. They all just plain end.

It looks even more ridiculous on the map, like 13 arrows shot at a target from random angles.

If all the streets led somewhere, they might be forgivable.But they all dead-end on either edge of a small forest. The result is that one can toss a stone over the trees, from Balboa Street in Capitol Heights onto Fitch Street SE - and then spend five minutes doing loop-de-loops in a car before one can retrieve it.

Then there is the question of law enforcement.

Let's say you have the bad luck to smash your car into another in the northernmost lane of Western Avenue. Whose case is it?

Not ours, said a spokesman for the D.C. police. If it had been in the southernmost lanes, yes, but the northermost belong to Montgomery County.

No chance, said a spokesman for the Montgomery County police. The actual border lies 35 feet northwest of the Western Avenue roadway. So anything anywhere along Western is the District's.

What happens in practice? Both departments say they handle Western Avenue as a place where either has jurisdiction. Prince George's says they and the city handle Southern Avenue the same way.

But the fun really begins at the Van Buren Street NE and Takoma Park's Second Street. That is the only place where Washington, Montgomery and Prince George's have a common border. It must be a very dangerous place, what with all the police cars making U-turns all the time.

So if you're worried about crime, the safest place in the Washington area has to be the median strip of Southern, Eastern or Western Avenue. But if you're worried about why three police departments haven't decided after 187 years whose turf is whose . . . well, so am I.

Then there is the ever-present issue of taxes.

It's actually not much of an issue. According to surveyor's records, the Montgomery County police are right. All around Washington, the border lies 35 feet outside the pavements of Southern, Eastern and Western Avenues.

For tax purposes, however, those three roadways are considered the border. So if you live in the "twilight zone" - that 35-feet strip tha rings the city - you pay tax to Maryland.

Around most of the city, homes are built right up to curbs of the three "directional avenues." But in the 4200 block of Southern, a group of homes sits in a neat row, exactly 35 feet back from the pavement.

None of the present residents knows why, and none said they care. But none had the attitude of a neighbor in the next block. His home sits right on the lip of Southern Avenue. Asked if the District has ever tried to tap him for taxes, the man said, "I don't pay taxes to nobody," and firmly slammed hi door.

Eyesores? The District's border has produced a honey in the 6500 and 6600 blocks of Eastern Avenue.

The old Eastern Avenue used to run along the foot of a steep hill that slopes upward into the city. But in 1947, the D.C. Highway Department decided to widen the street. To do so, they elected to build a new Eastern Avenue into the side of the hill, about 50 feet above and 25 feet west of the old.

The result? Homeowners on the D.C. edge of the new road had to build retaining walls so their front yards would not slide downhill. And homeowners on the Maryland side suddenly had a different view from their front porches. There, in all its glory, was a stark, gray, 50-foot-high concrete wall built to support the new road.

Both the retaining walls and the wondrous view from the Maryland side remain to this day. Ah, progress.

Virginia solved the District border problem in a rather practical way. Thirty-six of its square miles had once rested within the D.C. diamond. The state argued that the diamond was unworkable, random, ugly and unnecessary, and that the state needed the tax benefits from the land it once gave away.

Finally, in 1846, probably out of exhaustion, Congress gave Virginia back its land. The tract now comprises all of Arlington and much of Alexandria.

It's too much to hope that Maryland would wage, or could win, a similar land-grab effort. After all, the Free State has plenty of border problems already.

Its border with Delaware looks like it was chosen by some guy who said aw-the-heck-with-it. And why that last little slice of western Maryland isn't a slice of West Virginia is a perpetual puzzle.

I say, citizens, that we should look at it the other way. Let Washington grow larger. Let it redefine itself as all the area inside the Beltway.

Just warn me before the first car crash in the outer lanes. I hate the same old problems.