The first Labor Day celebration in the United States took place in New York City in 1882. On September 5 of that year, according to the Bowery Boys, New Yorkers marched from City Hall to 42nd Street, with a brief stop at Union Square, and continued on to the Upper West Side. The contingent stopped at Wendel's Elm Park, which was then the city's largest green space, at 92nd Street and Ninth Avenue (now Columbus Avenue, pictured), for a picnic. [Photo via Google Maps]

The storied college's meeting room has seen plenty of important speeches over the years, including Abraham Lincoln's 1860 speech that helped catapult him to the presidency. But one of its best-known addresses was rather brief: In 1909, in the midst of discussions among garment workers about whether to stage an industry-wide walk-out, 23-year-old Clara Lemlich delivered these immortal words: "I move that we go on a general strike." She had participated in walk-outs from the Triangle Shirtwaist Factory previously, and her remarks are seen as the catalyst for the Uprising of the 20,000, which lasted for several months. [Photo via MCNY]

Before this castle-like structure was became a branch of the New York Public Library, it served as a courthouse. (Rather infamously, it's where Stanford White's murderer, Harry Kendall Thaw, was ultimately found not guilty by reason of insanity during "the trial of the century.") Many women who participated in the 1909 walkout from the Triangle Shirtwaist Factory were brought here and tried in the night court, in the hope that they would be scared straight; it didn't work, and the protests continued. [Photo via Library of Congress]

This Lower East Side structure is where the Jewish Daily Forward was located for many years, including during a period where it became associated with New York's Socialist and labor movements. Under the editorship of Abraham Cahan, one of the paper's founders, the daily reported on labor activities and gave money to workers' causes and charities. [Photo via Joel Raskin/Curbed Flickr Pool]

This school was established in 1906, and though it functioned primarily as a hub for NYC's Socialist movement, it was also closely associated with many of the trade unions that were active in the labor movement, such as International Ladies' Garment Workers Union. It was located in this brick building near Union Square, and its archives were later folded into NYU's Robert F. Wagner Labor Archives. [Photo via Google Maps]

Webster Hall hosted labor rallies alongside weddings and lectures from the time it was built in 1886, but rose to prominence as a site associated with the labor movement after a 1913 fund raiser for the socialist magazine The Masses (who later took to calling the hall the Devil's Playhouse.) Labor rights activists like Samuel Gompers, Emma Goldman, and Margaret Sanger all made stops here to speak on prominent labor and civil rights issues.

Union Square hosted the first May Day parade—and that's not the holiday of Maypoles and cake. In the late 19th century, May 1 was chosen as International Workers' Day to commemorate the Haymarket affair, the bombing of a labor rally in Chicago that took place in 1886. During the parade, some 10,000 people gathered in peaceful strike advocating for an eight-hour workday. [Photo via MCNY]

During the construction of the Brooklyn Bridge, the workers in charge of digging the holes for its foundations—known as Sandhogs—went on strike due to dangerous labor conditions and unfair wages. The strike lasted three days but resulted in an increased wage of $2.75 a day for Sandhogs. [Image of the East River Bridge under construction in 1877 via MCNY]

The Brooklyn Labor Lyceum, not to be confused with the Brooklyn Lyceum on Fourth Avenue, was a popular meeting place for Socialists in the early 20th century. A January 24, 1910 article in the New York Times recalls a meeting in the hall, "About 2,000 persons with Socialistic sympathies crowded the Labor Lyceum, 949 Willoughby Avenue, Brooklyn yesterday afternoon, while as many unable to get in waited outside to hear a debate on Socialism between Morris Hillquit and Prof. Isaac Franklin Russell of the New York University Law School." These days the building—of course—serves as apartments.

Beginning in the 1930s through the 1960s, the ILGWU grew exponentially. During this time, the ILGWU "ran successful organizing campaigns, won significant concessions from manufacturers, and expanded the elements of social unionism for which the union had become so well-known." It was during this time that the union left its headquarters in Union Square and relocated to 1710 Broadway (1943, to be exact). It was a smart move to relocate to larger space; union membership would soon peak in 1950.