Plans for a bridge connecting San Francisco and Marin County were more than a decade in the making when, on this day in 1933, construction finally began. For about a century before the bridge’s construction, ferries were the primary means of travel across the bay. Though the idea of a bridge was circulating as early as 1872, it wasn’t until the 1920s that people thought the idea was feasible, in terms of both bridge technology and costs. The final suspension design was the result of a collaboration among Joseph Strauss, Irving Morrow, Charles Alton Ellis, and Leon Moisseiff. The bridge opened with much fanfare in 1937; its 75th anniversary will…