It was a day when spring was no longer an April Fool.

The Pennsylvania Avenue Development Corp. couldn't believe its luck yesterday when it dedicated John Marshall Park at Fourth Street and Pennsylvania Avenue, the third of the projected five new Pennsylvania Avenue parks.

Henry A. Berliner, PADC chairman, observing a lunchtime crowd toasting in the sun, noted an array of spring rolls, croissants and barbecue awaiting the celebrants. He said that with recent expose's of who had lunch with whom, and who paid for what, "no one in Washington of any importance now will go to lunch unless it's in an open park with 3,000 other people."

In introducing Chief Justice Warren Burger, Berliner, an attorney, then pointed out: "We come here not to praise judicial philosophy but to bury some trees and flowers."

Burger, the main speaker, said Marshall was was "the greatest jurist in American history."

Burger's predecessor, according to a Columbia Historical Society plaque, lived on the site of the park in the 19th century, when rowhouses, hotels and offices enclosed the park and the adjacent Judiciary Square. The last rowhouses were razed, over the protests of their former owners, in 1969. Some who came to the dedication mourned the demolished rowhouses and were not comforted by grass and paving.

Carol Johnson, the landscape architect who planned the park, and Marion Pressley, her job captain, pointed out the sundial, copied from Marshall's home in Richmond. (Marshall's several-times-great-granddaughter, Mary Douthat Higgins, was on the podium.)

The sundial said firmly, "Noon." Adding an hour for daylight-savings time, it was right on the mark.

By 2 p.m., the judges, the planners and the celebrants had departed. A woman sat on a bench, reading a copy of the Congressional Record. Two young women lounged on the grass. Three men in hard hats sat on a wall.

David, Mary, Sarah and Liza Behrendt of Milwaukee came over from the National Gallery of Art too late for the speeches, but in time for the spring rolls. "It's the green spaces that make Washington great," said David Behrendt. "We feel comfortable here. It's a hometown sort of place."