To enter the country, a U.S. citizen must show a passport and a one-entry tourist card, which is valid for between 90 and 180 days.
For stays longer than 180 days, you must acquire a permanent residency or long-term visa by visiting the El Salvadorian embassy.
Requirements for approval include a passport with at least six months of validity left, a certified yellow fever vaccination document, and a letter of business inviting the expat to work in the country.