After a devastating fire in Boston in 1873, many factories relocated to Chelsea, just a mile away across the Mystic River. An inexpensive passenger ferry also made Chelsea a convenient destination for the rising number of immigrants arriving in Boston. With jobs and affordable housing, the city by the early twentieth century had grown from a summer retreat for the wealthy to one of the most densely populated cities in America. When fire struck again, this time in Chelsea on April 12, 1908, it demolished a large section of the city. Images of the fire, the rebuilding that followed, the Great Depression, the war years, and one of the biggest changes to face the city—the building of the Mystic River Bridge—are all contained in Chelsea in the 20th Century.