Labor Day in the United States, observed on the first Monday of September, traces its origins to the labor movements of the late 19th century that advocated for better working conditions. The holiday, first celebrated on September 5, 1882, in New York City, was proposed by labor leaders Peter J. McGuire and Matthew Maguire. By 1894, President Grover Cleveland signed it into law as a federal holiday amid labor unrest. The day honors the contributions of American workers to the country's prosperity. While initially celebrated with parades and demonstrations, its significance has evolved, now also marking the unofficial end of summer. Labor union membership, once pivotal to the holiday, has seen a decline since its peak in the 1950s.