This m/s was issued in 2006 commemorating 150 years of National Campaign Against Nicaraguan Pres.William Walker.
William Walker (1824–1860) was an American physician, lawyer, journalist and adventurer, who organized several private military expeditions into Latin America, with the intention of establishing English-speaking colonies under his personal control, an enterprise then known as "filibustering." Walker became president of the Republic of Nicaragua in 1856 and ruled until 1857, when he was defeated by a coalition of Central American armies. He was executed by the government of Honduras in 1860.
In Central American countries, the successful military campaign of 1856-1857 against William Walker became a source of national pride and identity, and it was later promoted by local historians and politicians as substitute for the war of independence that Central America had not experienced. April 11 is a Costa Rican national holiday in memory of Walker's defeat at Rivas. Juan Santamaría, who played a key role in that battle, is honored as the Costa Rican national hero.
The 65c stamp is from 2009 Children's Literature issue and the 10c stamp is from 2002 Pan-American Health Organization Centenary issue.