According to the United States Treasury, Abraham Lincoln was put on the penny in 1909 as part of the celebration of what would have been his 100th birthday. Before the Lincoln penny, portraits of real people were not used on American coins, with earlier pennies featuring an image of a woman representing liberty.
When he was president, Theodore Roosevelt wanted to redesign the coins currently in use in America. He commissioned the sculptor Augustus Saint-Gaudens to create the new coins, but Saint-Gaudens died before the work was finished. Roosevelt then saw a sculpted plaque by Victor David Brenner featuring President Lincoln's likeness and chose it as the new design for the coin. 25 million of the Lincoln coins were struck in anticipation for public demand, and it was officially issued to the public on Aug. 2, 1909. The original reverse side featured a pair of sheaves of wheat, and this design was updated in 1959 to depict an image of the Lincoln Memorial. The penny was changed again in 2010, replacing the memorial with a shield bearing the legend, "E Pluribus Unum" across the top. The front of the penny has not changed significantly since its original introduction, making it the longest-serving coin design in America and one of the most enduring coin designs in the world.