CHICAGO — Designating the country’s newest national monuments, President Barack Obama said Thursday that protecting places of natural beauty and historic significance is a truly American ideal.

Obama used the powers of the presidency to designate the Pullman National Monument in his hometown. The historic South Side neighborhood is where African-American railroad workers won a significant labor agreement in the 1930s that Obama said led to such protections as the 40-hour work week.“So this site is at the heart of what would become America’s labor movement,” he said.

Pullman workers also played a role in the rise of the black middle class.

Obama began his career as a community organizer nearby and said returning to designate the monument “brings back a lot of memories.”

Before leaving Washington, Obama signed a proclamation in the Oval Office designating the Browns Canyon National Monument in Colorado, a 21,000-acre site along the Arkansas River popular for whitewater rafting. In Chicago, he also announced designation of the Honouliuli National Monument in Hawaii, the site of an internment camp where Japanese-American citizens and prisoners of war were held during World War II.

The Pullman designation honors the neighborhood built by industrialist George Pullman in the 19th century for workers to manufacture luxurious railroad sleeping cars. The 203-acre Pullman site includes factories and buildings associated with the Pullman Palace Car Company, which was founded in 1867 and employed thousands of workers to construct and provide service on railroad cars. While the company employed a mostly white workforce to manufacture railroad cars, it hired former slaves to serve as porters, waiters and maids on its sleeping cars.

The railroad industry — Pullman in particular — was one of the largest employers of African-Americans in the United States by the early 1900s. Pullman workers played a major role in the rise of the black middle class and, through a labor agreement helped launch the civil rights movement of the 20th century, the White House said.