A former aide for Schaefer says he died at 6:30 p.m. Monday at his home at the Charlestown retirement community outside Baltimore.
The former Maryland governor, known for being colorful, outspoken and at a times combative, leaves a legacy of impressive public works projects.
He was mayor of Baltimore from 1971 to 1986 and earned a national reputation for overseeing the transformation of downtown from a gritty center of urban decay in to a tourist attraction.
Schaefer was hospitalized with pneumonia earlier in April and was released back to his home on April 5. The cause of his death is not yet known.
Gov. Martin O'Malley has ordered the Maryland state flag to be flown at half-staff effective immediately.