The present main structure was designed in French Renaissance Revival style and built of red brick with limestone trim. After it opened on December 17, 1900, the facilities proved to be able to barely handle the flood of immigrants that arrived in the years before World War I. Writer Louis Adamic came to America from Slovenia , then part of the Austro-Hungarian Empire in 1913 and described the night he and many other immigrants slept on bunk beds in a huge hall. Lacking a warm blanket, the young man "shivered, sleepless, all night, listening to snores" and dreams "in perhaps a dozen different languages". The facility was so large that the dining room could seat 1,000 people. It is reported that the island’s first immigrant to be processed through was a teenager named Annie Moore from County Cork in Ireland.

After its opening, Ellis Island was again expanded with landfill and additional structures were built. By the time it closed on November 12, 1954, twelve million immigrants had been processed by the U.S. Bureau of Immigration.