The Lincoln cent is the current one cent coin of the US Dollar. It was adopted in 1909, replacing the Indian head cent; its obverse, featuring a bust of Abraham Lincoln (to commemorate his centennial), has been in continuous usage, while its reverse was changed in 1959 to its current design which includes the Lincoln Memorial (to commemorate Lincoln's sesquicentennial). There are more one-cent coins produced than any other denomination, which makes the Lincoln cent a familiar item. In its life span, this coin has weathered two world conflicts, one of which changed it materially, because metals play a vital part in any war effort. The obverse is the longest design used for any circulating American design.