he famous painting by Charles Sheeler of the modern Ford motor plant in River Rouge, Mich., was auctioned at Sotheby's today for $1.87 million, setting a record price for a 20th-century American work of art. (The previous record, set only three weeks ago, was $1.2 million for Willem de Kooning's "Two Women.")

"Classic Landscape" (1931) is an idealized depiction of the River Rouge "super plant" (once the world's largest, covering more than 16 million square feet) without the grime or toil generally associated with manufacturing. It was the culmination of Sheeler's commission from Henry Ford that started with a series of photographs of the plant in 1927. The Eleanor and Edsel Ford House Foundation consigned the painting for sale. It was purchased by three leading American-art dealers: Meredith Long of the Long & Company Gallery in Houston; Stewart Feld of New York's Hirschl & Adler Gallery, and Lawrence Fleischman of Kennedy Gallery in New York.

The three dealers, who were standing together in the back of the crowded salesroom joking with one another in the blush of their success, said they intended to sell the painting, which they believe to be one of a dozen or so great American paintings. Why did they buy it together? "Because we like each other," quipped Fleischman. "I'm short on change," said Feld.

"Classic Landscape" was the top work in a sale of American art here in Sotheby's ultramodern salesroom. A full range of works were offered, from 18th-century folk art to 20th-century precisionist art (such as the Sheeler). All the key works sold for solid prices, and only 10 percent of the offerings failed to sell. The total, nearly $11 million, was a record for a sale of American art. Records also were set in several other categories, including for works by Alfred Bierstadt and for John Frederick Kensett.

American painting sales generally are festive affairs, and this one was particularly so. With nearly 1,000 persons crowded into the room, and with auction madness having made a dramatic comeback two weeks ago, there was much excitement, anticipation and lots of humor to break the pace.

Bierstadt's "The Last of the Buffalo," which is similar to a painting with the same title in the Corcoran Gallery of Art, was sold for $792,000 to an unidentified midwestern collector--following a heated bidding battle during which a Texan dressed in a gray suit with matching cowboy boots called out his own bids from the floor.

Kensett's "On the Coast" (1870), which depicts an eastern coastline, fetched $269,000, outstripping its $70,000 to $100,000 presale estimate.

A Sheeler drawing, "Tulips" (1931), was bought by Hirschl & Adler Gallery for $190,000, setting a record price for an American drawing.

The most unusual item of the day was the sale of a Frederic Edwin Church painting. The original owner, so the story goes, had wanted a painting by Winslow Homer rather than by Church. So he simply had the signature changed. And for years the family referred to it as "Our Homer"--apparently not realizing that the painting, which depicts a rocky coastline, bears little resemblance to any of Homer's works. It was correctly identified last spring by a Sotheby's expert. "Coast of Maine" (1851) fetched $220,000.