Why are there so many spanish speakers in the US?

Many Latin Americans immigrate to the United States and the majority of them speak Spanish as their first language.

The US has had Immigration from a number of Spanish-speaking areas, notably Latin America (which was colonized by Spain) including Mexico and Puerto Rico (a US commonwealth). The Southwest US especially has many Spanish-speaking residents, some newly arrived but some descended from the original settlers of Greater Mexico in the 17th and 18th centuries.