More than 50 years after J. Willard Marriott opened his first business in the District and 25 years after his company started work on its first hotel in Northern Virginia, Marriott Corp. will open its first hotel in the city this week.

It is a significant step, for Marriott has become the fastest-growing hotel corporation in the world. And yet the firm's absence from the hotel business of its hometown has long been a subject of concern to some Washington business leaders, though Marriott has had many restaurant and food-production operations in the city.

As is typical when Marriott opens a new hotel, a lot of hoopla is planned for the ceremonies starting at 10:45 a.m. Tuesday, at the Washington Marriott, 22d and M streets NW.

In addition, a lot of hoopla not planned by Marriott has been promised by organized labor.

Demostrations are planned by Washington labor leaders to coincide with the grand opening, to protests Marriott's long tradition of nonunion operations. Similar union protests greeted the opening of Marriott's first hotel in downtown Chicago several years ago, but the unions failed to win support from the hotel workers.

Unions here also have objected in advance to the choice of Marriott to run a big new hotel on Pennsylvania Avenue, part of the major redevelopment on that historic street.

In an interview last week, native Washingtonian J.W. (Bill) Marriott Jr., the founder's son and company president, expressed little concern about a prospective union confrontation tomorrow or in weeks to come. Since his workers get "the same wages" as union people elsewhere, it is unlikely that a union would be successful in an organizing drive, he stated.

The same philosophy has guided Marriott managment over the years, and there have been remarkably few union confrontaions for a company of Marriott's size. From Marriott's first root beer stand on 14th Street NW, the Bethesda company has grown to annual sales of $1.72 billion in the year ended Jan. 2.

Bill Marriott said last week that sales this year should approach or surpass $2 billion, as the company opens a record 22 hotel across the country or overseas.

At this time 25 years ago, Marriott was overseeing initial construction work on the first hotel venture for his father's company, the Twin Bridges in Virginia with 350 rooms. That unit opened in January 1957 as the "world's largest motel," with 350 rooms (since enlarged to 450 and the site this year of Marriott's annual meeting.)

Tomorrow, Marriott will open the company's 82d hotel, with 350 rooms.The new, nine-story building was constructed in an "L" shape over and around Blackie's House of Beef, the 35-year old anchor restaurant of Ulysses G. "Blackie" Auger's local restaurant empire. Auger owns the hotel and Marriott will operate and manage it under a contract.

With the addition of this hotel, Marriott will have 2,700 hotel rooms in its metorpolitan-area operations, more than in any other city. New Marriott units in Gaithersburg and on Pennsylvania Avenue will add to Marriott's local presence in the next couple of years.

About 10,000 persons are employed locally by Marriott, with the firm's local payroll adding up to $100 million a year.

Marriott said last week that his initial experience with hotels 25 years ago convinced him that the company should expand in that business, "because more money could be made than from operating restaurants . . . the scale is so much bigger ant it has been easier to attract [quality] management in the hotel business than restaurants."

Although Marriott did expand gradually in hotels over susequent years, the current management concentration on the business as the company's major expansion sector came only in recent years. Now, Marriott plans to add 10,000 hotel rooms a year for the next five years and that rate of expansion will make the local firm the fourth largest hotel operator in the world by 1985.

Although Marriott once shunned downtown sites, big hotels are open today in such cities as Chicago and New Orleans. Major new convention-size hotels are being built or planned for Atlanta, Boston, San Francisco and New York.

Last year, Marriott hotel profits rose 17 percent on a 21 percent increase in revenues as average occupancy rates remained in the 80 percent range, among the highest anywhere. Hotel room capacity expanded 13 percent last year and this year's planned openings will boost total capacity another 38 percent.

Overall last year, Marriott earnings were flat at $72 million vs. $71 million, primarily because of interest expenses associated with the repurchase of 7.9 million shares of its own stock in the year.

Marriott said business in recent weeks has been "reasonably strong," with some evidence that consumers are beginning to "feel better" in the wake of Reagan administration programs to cut federal spending and revive real economic growth -- programs Marriott supports strongly. He also revealed that the company has launched a year-long study of its restaurant operations, to determine where Marriott should be in future years.