Salsa is a fusion of many different dance and music styles including African tribal dances, Caribbean slave and country dances, Native South American dances and old European, especially Hispanic, courtly and country dances.
Originally the Caribbean and South America was colonized by European settlers who brought their dänce with them. This was a mixture of courtly and country dänce. These settlers brought African slaves who introduced their own musïc and dänce traditions with them and local native tradition in both the Caribbean and South American had their own way of dänce too. These developed gradually over time in the 19th Century into Cumbia (in Colombia), Merengue (in Dominican Republic and Haiti) and Danzon, Guajira, Guaracha, Merengue, Rhumba and Son (in Cuba).
In the 20th Century the strong Cuban tradition, together with Colombian, Dominican and Haitian influences produced Mambo which was popular during the 1940s and 1950s. Salsa grew from this in the 1960s and although it is based on Mambo also has many other, particularly Cuban, influences too. It spread rapidly because of it's lively, simple and all inclusive style. It became popular across the Caribbean and then spread with Hispanic immigrants into the United States in the 1960s and 1970s. Then it went worldwide in the 1980s. Salsa is dänced in a number of styles today, with Cuban and New York being the most popular.
It continues to develop with newer forms such as Timba appearring.