The United States Mint's Presidential Medals date back to the earliest days of the Republic. Medals were presented to American Indian chiefs and other important leaders at events like treaty signings. Bronze (mixed copper and zinc) replica presidential medals are available for sale to the public through the United States Mint's online catalog. Lewis and Clark, on their expedition to the Pacific coast between 1804 and 1806, carried a supply of these ''Indian Peace Medals.'' They presented these medals, bearing the portrait of then-president Thomas Jefferson, to important chiefs. The peace medal tradition continued into the middle of that century. The peace medal series became the Presidential medal series after President Andrew Johnson left office in 1869. The front of each medal continued to bear a portrait of the incumbent president. On the back, instead of symbols of peace and friendship, were inaugural dates, terms of office, presidential symbols and seals, and excerpts from speeches.