King Park underwent several alterations in the early and mid-20th century, and there were numerous unexecuted plans to demolish the mansion or convert it to other uses.

[7] The park covers 11.5 acres (4.7 ha)[8] and preserves a portion of the former estate of Rufus King, one of the Founding Fathers of the United States.

The current park site was located between a group of hills named the Woody Heights to the north and Mechawanienck Trail (which later became Jamaica Avenue) to the south.

[27] Other sources date King Manor to 1750,[28][29][30] although the New York City Landmarks Preservation Commission (LPC) cites the western half of the house as having been built at that time.

[18] A later pastor for Grace Church wrote that the farm was surrounded by a fence and included a fruit orchard that was capable of producing 100 barrels of cider annually.

[71] The manor was inherited by his firstborn son, John Alsop King, who would later serve as a state legislator, U.S. Representative, and then the governor of New York.

[85] Nonetheless, the village trustees acquired the land on July 9 and opened it to the public; they also appointed a policeman to serve as the house's live-in caretaker.

[86] A New York Supreme Court justice enjoined the trustees from spending money on the park's upkeep,[87] but the Appellate Division reversed this injunction.

[105] By March, the Daughters of the American Revolution (DAR), the Jamaica Women's Club, and the Brooklyn Public Library Association planned to refurbish the first-floor rooms,[104][106] although this was delayed because a furnace in the mansion had to be repaired first.

[113] Brooklyn Life magazine wrote that the conversion of King Manor into a clubhouse was "doubly gratifying", as many of western Long Island's old structures were being demolished.

[139][145] Additional clubs had space at the house during the late 1910s, including the National Surgical Dressings Committee[146] and the DAR's Rufus King Chapter.

[151] This prompted opposition from several civic groups led by the DAR's King chapter,[150][152] and the KMA received numerous letters speaking out against the library plan.

[158] Pratt Institute artisans also took wood from an old oak tree on the grounds and turned it into three gavels, which were presented to the DAR, KMA, and American Scenic and Historic Preservation Society in 1921.

[211] King Manor was one of the founding members of the Historic House Trust, established in 1989,[212][213] and the city gave $28,000 for programs at the mansion the same year.

[214] Roy Fox, a former radio host who was looking for a place to live, became the house's caretaker in 1989 after learning about a rent-free apartment from his wife's supervisor.

[217] Museum officials developed a plan for the house's programming in 1991 after the Andy Warhol Foundation and J. M. Kaplan Fund provided a $50,000 grant.

The project included new doors, shutters, and windows; repairs to the wooden porch, which had been restored in the 1990s but was starting to buckle; repainting of the facade; and upgrades to the air conditioning, lighting, and fire detectors.

[229][230] The project included drainage upgrades, drinking fountains, a turf field, and a concert space in the park, as well as new trees and driveway at the mansion.

[235] The mansion was closed temporarily in 2020 due to the COVID-19 pandemic in New York City; Roy Fox, who had been the live-in caretaker for three decades, continued to maintain the property.

[234] Nonetheless, King Manor officials claimed in 2023 that the house was suffering from neglect: its exterior had not been repainted in two decades, while the dining room was partly closed because of falling plaster.

[94] The parlor, at the southwest corner of the house, has a gray-and-white marble fireplace mantel, which was added in the late 1820s and was designed in the Greek Revival style.

[244] The parlor also has a paneled door; a plaster wall with baseboard and chair rail; six-over-six sash windows; and a cornice with moldings, dentils, and Greek frets.

[245] At the eastern end of the main house, a short flight of steps lead down to the former children's playroom, which has a closet and walls with paneling.

[25] The KMA encouraged people to lend or donate Colonial-style objects;[260] in its first decade, the association loaned or acquired artwork, furnishings, carpets, engravings, and bric-à-brac.

Other parts of the house displayed objects like kitchen utensils, porcelain, tableware, Rufus King's desk, a four-poster bed, and a portrait of 18th-century resident Mary Colgan.

[254] The house also contains original artifacts, such as an 18th-century piano built in England[248] and an old leather horse-hair sofa under the west window that belonged to Rufus King.

[247] To attract visitors after the 1990s renovation, the museum began posting bilingual signs and hosting events in both English and Spanish,[221] and the parlor and other first-floor rooms were used as meeting spaces.

[74] The Standard Union said in 1900 that the house "bears comparatively few traces of the many winters it has weathered" and credited its sturdy construction to the fact that it was built by hand.

[29] The Brooklyn Daily Eagle said in 1907 that, despite its nondescript appearance, King Manor was "one of the show places of Jamaica";[100] a 1913 article from the same newspaper said the house reflected "the individuality of its former owners".

[254] In spite of this, the Daily News wrote in 2009 that the house was "far down the list of the city's favorite tourist sites" because King's roles as a senator and diplomat were relatively obscure.