In the 1930s, under parks commissioner Robert Moses's West Side improvement project, the railroad track was covered with an esplanade and several recreational facilities.

The 191 acres (77 ha) of land in the original park between 72nd and 125th Streets[a] were once inhabited by the Lenape people, but by the 18th century, European settlers used it for farming.

However, development in the neighborhood was slow to come since most of the lots were too expensive for the middle class to purchase, and the wealthy preferred to settle on the East Side of Manhattan.

[32] Under an act of the state legislature, the city condemned an underwater area along the shore, which would allow for land reclamation to expand the park.

This clashed with the ideals of the City Beautiful movement, which led an increasing segment of the population to view the railroad as a nuisance rather than a part of the park.

The area between 59th and 72nd Streets was being planned for development into train yards, which citizens' groups strongly opposed,[56] and the city had no money to condemn that land.

[60][63] The same year, comptroller Charles L. Craig put forth a plan to create a waterfront parkway in Riverside Drive to alleviate vehicular traffic.

In order to meet the requirements of the project, the firm proposed erecting a City Beautiful-style retaining wall with arches, similar to that of a Roman aqueduct, that seemed to support the highway above it.

Moses halted McKim, Mead & White's plan,[75] deriding it as a "visionary scheme,"[74] since he thought the highway's construction would make the new parkland inaccessible and contain too many pedestrian tunnels.

The 'park' was nothing but a vast low-lying mass of dirt and mud.... Unpainted, rusting, jagged wire fences along the tracks barred the city from its waterfront ...

The engines that pulled trains along the tracks burned coal or oil; from their smokestacks a dense black smog rose toward the apartment houses, coating windowsills with grit ... [a stench] seemed to hang over Riverside Drive endlessly after each passage of a train carrying south to the slaughterhouses in downtown Manhattan carload after carload of cattle and pigs.... [Once, Frances Perkins ] heard Moses exclaim, "Isn't this a temptation to you?

[101] The construction of Westway within Riverside Park was ultimately deemed infeasible due to a state law that prohibited the Henry Hudson Parkway's conversion into an interstate highway.

The failed Westway proposal had inspired a movement to make Riverside Park a designated city landmark, so as to preclude future construction that might take away parkland.

[104] Riverside Park was designated as a New York City scenic landmark in 1980[105] and listed on the National Register of Historic Places (NRHP) in 1983.

[107] The organization soon turned toward preservation-oriented initiatives, successfully working to stop July 4 fireworks shows in the park and plans for a restaurant at the 79th Street Boat Basin.

[118] The North River Wastewater Treatment Plant was constructed between 137th and 144th Streets, alongside Riverside Park's northern section, during the late 1980s.

[121] In the 1980s Donald Trump, then the owner of the 57 acres (230,000 m2) of land just south of Riverside Park that had been the Penn Central freight rail yard, proposed building a massive development including a huge shopping mall and the world's tallest skyscraper.

[122] Facing great opposition and hobbled by his weak financial position, Trump agreed in 1990 to adopt a new plan for the site put forward by six civic groups.

In order to expand Riverside Park by 25 acres (100,000 m2), Trump's proposed shopping mall would be eliminated and the elevated West Side Highway would be relocated eastward to grade and buried.

This was attributed to the economic conditions in the neighborhoods adjoining each section: while the Upper West Side was generally wealthy, Harlem was mostly lower-class.

[132] In 2015, after a quarter-century of planning, construction started on a new pedestrian bridge connecting Hamilton Heights to Riverside Park at 151st Street, replacing a tunnel and a long staircase.

[148][149] The Henry Hudson Parkway, on the park's western border, contains numerous interchanges that are included as part of the official landmark designation.

The central sections, comprising both the sloping region and the plateau above the Freedom Tunnel, contain most of the greenery as well as playgrounds and other recreational facilities.

One side of the monument reads: "Erected to the Memory of an Amiable Child, St. Claire Pollock, Died 15 July 1797 in the Fifth Year of His Age.

The architect Michael Dwyer designed inscriptions in the surrounding granite pavement, including a quotation from Roosevelt's 1958 speech at the United Nations advocating universal human rights, and a bronze tablet, located in the planting bed, summarizing her achievements.

[168][173] The architect Harold Van Buren Magonigle designed the monument as a sarcophagus in Tennessee marble, with a dedicatory inscription on the east side.

Karl Bitter sculpted the centerpiece, an equestrian statue of Sigel, who attained the rank of general in the Union Army during the Civil War.

[37][150] Originally planned for Grand Army Plaza in Brooklyn,[164] the monument was erected in Riverside Park opposite West 89th Street.

[183] A granite plaque, set in the paving at the end of the Promenade, near 84th Street, on October 19, 1947, is inscribed: "This is the site for the American memorial to the heroes of the Warsaw Ghetto Battle April–May 1943 and to the six million Jews of Europe martyred in the cause of human liberty.

[212] Riverside Park's numerous recreation facilities include tennis, volleyball and basketball courts; soccer fields; and a skatepark.