Construction of the Empire State Building began in March 1930. The project involved 3,400 workers, mostly immigrants from Europe, along with hundreds of Mohawk iron workers, many from the Kahnawake reserve near Montreal. According to official accounts, five workers died during the construction. Construction was ready in May 1931.
The dangerous nature of constructing what was then the world's tallest building can be seen in these photos from the New York Public Library's collection.