He is chiefly remembered for his urban renewal efforts in Pittsburgh, undertaken in an unlikely bipartisan (Mellon was a lifelong Republican) partnership with the city's postwar Democratic mayor David L. Lawrence.

After returning to the city following World War II, Mellon developed an interest in improving Pittsburgh's severe flooding, pollution, and urban blight.

[3] Mellon served as Vice President of American Council to Improve Our Neighborhoods, an organization to promote for-profit private urban renewal projects.

The Richard King Mellon Foundation manages his charitable estate and has recently participated in redeveloping industrial brownfields in Pittsburgh.

[6] In 2001 the foundation donated two tracts of land, totaling 61,633 acres, to the Louisiana Department of Wildlife and Fisheries (LDWF) for the Maurepas Swamp WMA.