This week's Real History documentary focuses on the history of the Bay Bridge in San Francisco, a historic marvel of engineering that at the time it was built used all steel made in the United States. Celebrating its 75^th anniversary this year, the city wanted to use only American steel to upgrade the bridge. However, the upgrade will need some steel parts from China that contractors say are not made in the United States, and now the Alliance for American Manufacturing is up in arms that the bridge will now longer be 100 percent American steel. Watch the documentary below on the history of the Bay Bridge and the challenges it now faces: