Twin Bridges was either named for the two bridges that spanned the Jefferson River nearby, or for two bridges over the Beaverhead and Big Hole Rivers built by the Lott brothers in 1865. The town is near the confluence of the tributaries of the Jefferson River, which were named by Lewis and Clark in 1805. The explorers chose to commemorate the “three cardinal virtues” of President Thomas Jefferson with the names Philosophy, Wisdom and Philanthropy. These small rivers were later renamed, respectively, the Beaverhead, the Big Hole, and the Ruby. Twin Bridges is not far from Beaverhead Rock State Park. Sacajawea recognized this huge landmark, resembling the head of a swimming beaver, while traveling with the Lewis and Clark Expedition in 1805.