The first indigenous peoples of Costa Rica were hunters and gatherers, and when the Spanish conquerors arrived, Costa Rica was divided in two distinct cultural areas due to its geographical location in the Intermediate Area, between Mesoamerican and the Andean cultures, with influences of both cultures.
William Walker was an American physician, lawyer, journalist and mercenary who organized several private military expeditions into Mexico and Central America with the intention of occupying the local nations and establishing slave-hold colonies, an enterprise then known as "filibustering". Walker usurped the presidency of Nicaragua in July 1856 at the request of Liberal Democratic Party of Nicaragua and ruled until May 1, 1857, when he was forced out of the presidency and the country by a coalition of Central American armies. He returned in an attempt to re-establish his control of the region, but was captured and executed by the government of Honduras in 1860 while escaping the Costa Rican army after being defeated by General Cañas in the battles of Rivas and Santa Rosa.
Juan Rafael Mora Porras was President of Costa Rica from 1849 to 1859.
Juan Santamaría Rodríguez was a drummer in the Costa Rican army, officially recognized as the national hero of his country for his actions in the 1856 Second Battle of Rivas, in the Filibuster War. He died in the battle carrying a torch he used to light the enemy stronghold on fire, securing a victory for Costa Rica against American mercenary William Walker and his imperialist forces. Thirty five years after his death, he began to be idealized and was used as a propaganda tool to inspire Costa Rican nationalism. A national holiday in Costa Rica, Juan Santamaría Day, is held annually on April 11th to commemorate his death.
Alajuela is a district in the Alajuela canton of the Alajuela Province of Costa Rica. As the seat of the Municipality of Alajuela canton, it is awarded the status of city. By virtue of being the city of the first canton of the province, it is also the capital of the Province of Alajuela.
Patricio Rivas (1810–1867), a wealthy Nicaraguan lawyer, was Acting President of Nicaragua from June 30, 1839 to July 27, 1839 and from September 21, 1840 to March 4, 1841. Later he served as a President of one of the several competing governments of Nicaragua from October 30, 1855 to June 24, 1857. However, he was merely a puppet president; rule was held by William Walker. He belonged to the Democratic Party.
In the 19th century, Nicaragua was beset by political problems, allowing William Walker, an American Southerner seeking to establish English-speaking slavery states in Latin America, to ascend to the Nicaraguan presidency.
The Second Battle of Rivas occurred on 11 April 1856 between Costa Rican militia under General Mora and the Nicaraguan forces of American mercenary William Walker. The lesser known First Battle of Rivas took place on the 29 June 1855 between Walker's forces and the forces of the Chamorro government of Nicaragua.
Greytown, formerly known as San Juan del Norte or San Juan de Nicaragua, is a town and municipality in the Río San Juan Department of Nicaragua.
The Filibuster War or Walker affair was a military conflict between filibustering multinational troops stationed in Nicaragua and a coalition of Central American armies. An American mercenary William Walker invaded Nicaragua in 1855 with a small private army. He seized control of the country by 1856, but was ousted the following year.
José María Cañas Escamilla was a Costa Rican military figure. He was born in Suchitoto, El Salvador.
Francisco Castellón Sanabria was president of "Democratic" Nicaragua from 1854 to 1855 during the Granada-León civil war.
The First Battle of Rivas occurred on June 29, 1855, as part of the struggle to resist William Walker, an American filibuster, adventurer and mercenary who arrived in Nicaragua with a small army of mercenaries in June 1855 in support of the Liberal democratic government of General Francisco Castellón in the Nicaraguan civil war. His army, with local support, was able to defeat the Legitimist party (Aristocratic) and conclude the Nicaraguan civil war.
Charles Frederick Henningsen was a Belgian-American writer, mercenary, filibuster, and munitions expert. He participated in revolutions and civil wars in Spain, Circassia, Hungary, Nicaragua, and the United States.
John Edward Hollenbeck was an American businessman and investor who was involved in the 19th century development of Nicaragua and the city of Los Angeles, California.
Between 1665 and 1857, Caribbean pirates and filibusters operated in Lake Nicaragua and the surrounding shores. The Spanish city of Granada, located on the lake, was an important trading centre for much of its early history so it was a prime target for pirates such as Welshman Henry Morgan and freebooters like William Walker.
National Border Route 1856, whose official name is Ruta Juan Rafael Mora Porras, and is also known as trocha fronteriza, is an abandoned dirt road in Costa Rica on the south bank of the San Juan River.
The Battle of La Virgen occurred on 3 September, 1855, at La Virgen, Nicaragua. It was part of the Legitimist efforts to resist the newly arrived force of William Walker, who had the support of the fierce opponents of the Legitimists, the Democrats. After a hard-fought but one-sided skirmish, Walker's forces emerged victorious, giving the cause of the invading Filibuster army legitimacy, and inspiring many new volunteers to join his force.
The Battle of Masaya took place in the small town of Masaya, northwest of William Walker’s filibuster capital, Granada. It was part of Walker’s efforts to dislodge the resurgent Allied Central American Army from its fortifications in Masaya, which lay within a day’s march of his capital. After significant initial filibuster advances were made, Walker’s army was forced to retreat towards Granada after receiving notice that the city was under attack.
The Second Battle of Masaya took place in the town of Masaya, northwest of William Walker’s filibuster capital, Granada. Having fought an inconclusive battle there the previous month, Walker again aimed to capture the valuable fortified town. The assault and subsequent siege of the town was inconclusive, as the heavy losses suffered on both sides still did not produce a definitive result, with Walker’s men withdrawing back to Granada after three days and nights of fighting. This loss drove Walker to not only abandon his vulnerable capital at Granada, but also to burn it to the ground.
Filibusters 
Costa Rica 
Lt. Callender I. Fayssoux