CONCORD, Mass. (AP) _ Robert Lowell Moore, co-founder of the Sheraton Hotel chain, has died at age 90.

Moore, who died Wednesday, began buying depressed real estate, including two hotels, in 1934 with his Harvard University roommate Ernest Henderson.

A third hotel, the Sheraton in Boston, was bought for back taxes owed the city. Because of the large electric sign on the roof advertising the hotel, the pair took its name for future sites, according to a history of the chain provided by Moore's son, Robin.

The chain, based on failing hotels, prospered during the early days of World War II.

Moore, who served as an ambulance driver and aviator in World War I, turned down a commission in the Army Air Force for World War II, telling the government he could be of more help working with William Lear in development of the wire recorder and Radio Direction Finder, a navigational device.

The RDF conceived and manufactured by Moore and Lear soon became standard equipment on all U.S. military aircraft.

In 1944, having resumed his relationship with Henderson, the two bought Boston's Copley Plaza hotel and continued building the Sheraton chain. In 1948, they merged with U.S. Realty and Improvement Corp., and the companies became Sheraton Corporation of America.

In 1967, Moore and Henderson began negotiations with International Telephone and Telegraph, which bought Sheraton in 1968. Henderson died during the negotitation period.

Moore, who graduated from MIT after his Harvard years were interrupted by World War I, was the co-founder of the Thoreau Lyceum in Concord, a museum and repository of Henry David Thoreau memorabilia.

Besides son Robin, he is survived by his wife, Eleanor, two sons, nine grandchildren and eight great-grandchildren. A memorial service will be scheduled at a later date.