JPMorgan Chase & Co. is seeking to sell 1 Chase Manhattan Plaza, the lower Manhattan tower built by David Rockefeller in the late 1950s.

The bank would relocate about 4,000 employees to other New York locations, said Brian Marchiony, a spokesman. JPMorgan occupies about half of the space in the 2.2 million-square-foot building.

An offering of the tower, a city landmark designed by architect Gordon Bunshaft, would test the downtown office market. Shrinking financial companies have left lower Manhattan landlords with at least 6.3 million square feet of space to fill, according to data from Newmark Knight Frank Grubb. The tower may achieve its highest value as a mixed-use property.

“You could do a department store in the base,” he said. “It’s a very exciting potential mixed-use opportunity,” said Dan Fasulo, of research firm Real Capital Analytics.