Built in 1891 to house both the government’s customs office and postal service and courts, this imposing four-story red-brick landmark alongside Mallory Square made an early mark as the site of inquiry into the sinking of the USS Maine in Havana harbor, which led the United States into the Spanish-American War. Since 1999 it’s been home to a bright, appealing museum showcasing local artists—especially Mario Sanchez, Key West’s answer to Grandma Moses—and exhibitions focusing on historical periods and events that defined and changed the island, including the arrival of the railroad, the hurricane of 1935, cigar making, the impact of Ernest Hemingway, and more.