Why and when did Labor Day become a federal holiday? 

In the 1880s, the emerging labor movement proposed a holiday to celebrate workers and give them a day off. Two union leaders, Matthew Maguire and Peter J. McGuire, took the lead. In 1887, Oregon became the first state to declare Labor Day a holiday. When Labor Day was made a national holiday in 1894 with the support of President Grover Cleveland, 30 states were already celebrating it.