Harlem Park started as one of the largest squares in West Baltimore, 9 ¾ acres, more than double the size of Franklin, Lafayette, or Union Square. The grounds of the park and much of the land around it had originally belonged to Dr. Thomas Edmondson.
Dr. Thomas Edmondson was born in 1808 as the son of a prosperous local merchant and graduated in medicine from the University of Maryland in 1834. He never practiced medicine and instead focused on art and horticulture, building a grand mansion and greenhouses on a hill now bounded by Edmondson Avenue, Harlem, Fulton and Mount. Dr. Edmondson died in 1856 and his estate presented a section of the property to the City of Baltimore on November 11, 1867 as a gift for the creation of a public park or square.
The city passed an ordinance accepting the gift in February 1868 and improvements on the park soon began. The engineer and general superintendent for Druid Hill Park, August Paul, prepared a plan for the grounds with "Beds and mounds of exotic and native flowers, the most difficult of cultivation" laid out in patterns of "stars, diamonds, Maltese crosses, hearts, ovals, circles, and semicircles, each one of great artistic beauty and of remarkably accurate outline." Another account described a "group of willows that encircled a gurgling spring at the eastern end of the grounds... a white mulberry tree that was a delight to the neighborhood, and a great flowering tree of the lobelia family, abundant in the Hawaiian Islands."
The park was dedicated in 1876, as an asset to the increasingly developed blocks around the park and up to Fulton Avenue. The Harlem Stage Coach Company incorporated in February 1878 to run a line of omnibus coaches from Fulton Avenue to Edmondson Avenue before turning south at Harlem Park. One of the directors of the enterprise was Joseph Cone, who became a tremendously active rowhouse builder in West Baltimore during the 1870s and 1880s, putting up hundreds of rowhouses each year with then modern amenities such as gaslights, hot water, central heating, and door bells. Cone pioneered the financing strategy of "advance credit" where home-owners could pay for their properties piecemeal providing the builder with capital for putting up yet more houses.
Harlem Park was substantially diminished in the early 1960s, with the construction of a $5,300,000 school complex, designed by architects Taylor & Fisher, resulting in the demolition of homes and businesses along the northern edge of the park. The school also took the eastern half of the park to turn it into a school yard. The remaining square endures as a quiet green space still used by West Baltimore residents.