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.