In the early 1940s, it was renamed after General Douglas MacArthur, and later designated City of Los Angeles Historic Cultural Monument #100.

Both Westlake and Eastlake (as well as Echo Park) were built as drinking water reservoirs connected to the city's system, Zanja Madre.

[15] For many years, Filipino World War II veterans protested in the park named after their former commander regarding promises made when they enlisted that the United States had reneged on.

Members of the Los Angeles Police Department then used batons and rubber bullets in a manner later found by the LAPD's own investigation, as well as by the courts, to be excessive.

[22] Beginning in 2002, the Los Angeles Police Department and business and community leaders led a redevelopment effort that has led to the installation of surveillance cameras, the opening of a recreation center, increased business, early-morning drink vendors, a new Metro station, the return of the paddle boats and the fountain, and large community festivals attracting thousands.

[23] In 2007, Levitt Pavilion Los Angeles opened, offering 50 free concerts each summer and attracting a wide range of audiences from around the country and globally.

Some of the artists involved were: Robert Williams, Skill, John "Zender" Estrada, Hector "Hex" Rios, Geo, Exit, Trip, Hate Prime, Relic, Galo "MAKE" Canote, RickOne and others.

Considered to be MS-13 territory, many poorer locals of the area, especially those doing illicit business in the park, are forced to pay a "tax" to the gang in exchange for being left alone.

In 2021, multiple attacks on transgender sex workers in the park had led to increased police presence and were widely reported.

MacArthur Park/Westlake Park and its boats figure prominently as the scene of a murder in the 1949 film noir Killer Bait (also known as Too Late for Tears) with Lizabeth Scott, Don DeFore, Dan Duryea and Arthur Kennedy.

The 1968 hit song MacArthur Park, written by Jimmy Webb and originally recorded by Richard Harris and later famously covered by Donna Summer, was inspired by this location.