For centuries, the major hospital of San Juan de Dios has been historically considered the first hospital in Aguascalientes,Mexico, founded on 1685. However, in this paper we report that the Hospital of the people of San Marcos, in operation at least since 1630, was really the first hospital in the state in functions and which services to the needy population continued until today’s last notice, as of 1728. As evidence, we offer various first-hand documentary sources obtained in different archive files, which give credit to this modest charity institution. The aforementioned for the memory and pride of the history of health care in Aguascalientes and Mexico.