This little museum close to the central park in Estelí is called the 'Asociación de ex-combatientes históricos 18 de Mayo' and is run by family of people who lost their lives during the revolution.
The Sandinistas found much support in Estelí, even before the revolution started. This is why the city has been tormented by the contras as well as by Somoza's army.
The museum is small but has many photographs, newspaper articles, and personal stories. Besides the revolution and the war, the political history of Nicaragua is also explained, part of it even in English. Entrance is free but a donation to the association is highly valued.
You can find the museum half a block South of the cathedral.