The story of WTTG-Channel 5, everyone stressed, is not that of an overnight success -- even though Washington's first television station is enjoying its best year and threw itself a 40th anniversary party last night that a nouveau riche Gatsby would have envied.

An army of congratulators surrounded John Kluge, chairman of the board of Metromedia, which owns WTTG, as he watched old shows flicker by on giant screens in the Pension Building and tried to explain WTTG's success.

"The growth reminds me of the New York detective who wrote 'The French Connection,' and someone marveled that he wrote it in six weeks. And he said, 'Yeah, six weeks and 20 years of rejection slips,' " Kluge chuckled. "It has been slow growth. We take one step forward and two steps back."

Whatever the hardships in the climb from the one microphone-one camera studio on the 12th floor of the Harrington Hotel, last night's gala with Tony Bennett celebrated the station's achievements. Some of them were statistical:

WTTG is the number one independent station in the country; it was the first station to broadcast a presidential inauguration; its "Panorama" is the longest running interview and TV news show in the city; it won Emmys last year for best newscast and best anchor -- Maury Povich.

And the latest ratings, said Metromedia senior vice president Bob Bennett, who created the 10 o'clock news program and "Panorama" in the late 1960s, show "we have a 20 rating from sign-on to sign-off. We outrate WRC, tie with WJLA and are only a few points behind WDVM. That is unheard of for an independent."

Some of the achievements were personal. Connie Chung, an anchor for NBC News and the wife of WTTG's Povich, started at the station as a "copy shlep" in 1969. When Lee Reynolds was mentioned and his image as Capt. Tug flashed on the giant screens, there was loud applause and reminiscing for one of the area's early children's characters.

Chung, Reynolds, Redskins star George Starke, Mayor Marion Barry and film producer Nancy Dickerson all had to share the spotlight with Jayne Kennedy, the TV personality whose exercise video is among the top five best sellers, and Ted Knight, whose "Too Close for Comfort" is one of Metromedia's most popular shows. Kennedy and Knight are doing the commentary for today's Cherry Blossom Parade, which, naturally, WTTG will carry.

Last night, the Pension Building resembled Tivoli Gardens, with gold branches decorated with lights around the marble pillars, along with round tables with gold cloths and votive lights and specially engraved champagne flutes.

Commenting on the lavishness and size of the gathering -- 1,300 guests -- Kevin O'Brien, WTTG general manager, said: "We are making a statement about the growth and prosperity of the nation's number one independent."

But probably the greatest tribute to endurance came from Thomas T. Goldsmith, the man who installed the first two antennas and put the station, then W3XWT, on the air in 1945. When the owner needed call letters, he chose Goldsmith's initials, and when the physics professor emeritus was introduced last night, he jumped the 4-foot rise to the stage.