The Bronx underwent rapid urban growth after World War I. Extensions of the New York City Subway contributed to the increase in population as thousands of immigrants came to the Bronx, resulting in a major boom in residential construction. Among these groups, many Irish Americans, Italian Americans and especially Jewish Americans settled here. In addition, French, German, Polish and other immigrants moved into the borough. The Jewish population also increased notably during this time. In 1937, according to Jewish organizations, 592,185 Jews lived in The Bronx (43.9% of the borough's population), while only 54,000 Jews lived in the borough in 2011. Many synagogues still stand in the Bronx, but most have been converted to other uses.