In 1851, the U.S. Congress made major changes to postage rates which required new stamps.The United States government issued two “Official” carrier stamps, the Franklin carrier (Scott LO1) and the eagle carrier (Scott LO2), to be valid in all major U.S. cities, unlike semi-official carrier stamps, which were only for use in the city in which they were issued. These new stamps were designed and printed by the Toppan, Carpenter, Casilear & Co Security printers. The September-issued LO1 was joined – or perhaps replaced – by LO2 in November, which saw widespread use for several years in American cities.