San Luis Potosí, city (1990 pop. 489,238), capital of San Luis Potosí state, central Mexico. Situated on a plain almost entirely surrounded by low mountains, the city is a mining and agricultural distribution center and a rail junction. Industries include foundries, smelters, and factories which produce clothing, leather goods, and beverages. Founded in 1576, San Luis Potosí was strategically important in colonial times and during the wars of the republican period. The patriot Francisco I. Madero, who was briefly imprisoned in the city in 1910, later named his revolutionary call to arms the Plan of San Luis Potosí. The city has narrow cobbled streets and solid colonial architecture. Among its major landmarks are the San Francisco convent and Carmelite churches.