Released on June 29th, the 150th Anniversary stamps commemorating the Transcontinental Railroad were issued in limited numbers will only be available "as supplies last." The set of three stamps bear images of the two locomotives that met at Promontory Summit, Utah: the Central Pacific's Jupiter and the Union Pacific’s No. 119, together with a smaller representation of the legendary "Golden Spike."
They are available only as part of an 18-stamp souvenir sheet:
From the 75th anniversary (1944):