This park and the neighboring playground, east of the BMT Brighton Beach transit line, are named for postmaster William E. Kelly (1872-1929). Born in Brooklyn, Kelly attended P.S. 9, P.S. 41, and evening high school. After graduating with honors, he worked as an errand boy at Harper Brothers publishers. He was also an amateur boxer. In 1894 Kelly was hired by the Kings County post office, then the sixth largest in the nation. He rose through the ranks. He was president of the National Letter Carriers Association from 1907 to 1913. He served as superintendent and assistant to the postmaster before President Woodrow Wilson appointed him as county postmaster. Kelly served in this position from March 1914 to December 1915. Kelly resigned as postmaster to serve as Clerk of Kings County, a public office, which he held from January 1916 until his death on September 20, 1929.