“Lost LA” is a historical documentary series that explores Southern California’s hidden past through documents, photos and other rare artifacts from the region’s libraries and archives. Hosted by writer Nathan Masters of the USC Libraries, each episode of “Lost LA” brings primary sources of L.A. history to the screen and connects them to the Los Angeles of today. Los Angeles is often thought of as a city without a history, an instant metropolis defined by the glitz and glamour of the entertainment industry. “Lost LA” challenges these assumptions, offering a history of Southern California. A co-production of KCET and the USC Libraries, “Lost LA” explains the Southern California of today and how the city got here.