Located in the downtown San AgustÍn Historic District, it was once the Republic of the Río Grande's capitol building. It now showcases memorabilia from the short-lived Republic of the Río Grande and displays pictures, books, and furniture from the 19th-century Laredo area. There are three restored rooms: an office and sitting area, a bedroom, and a kitchen. Casa Ortiz, part of this complex, is a state historic landmark.

The building is a Recorded Texas Historical Landmark and a Contributing Structure to the San Agustín National Register District. Along with its neighbors, San Agustín Cathedral and La Posada Hotel, the museum forms a triangle of the most visited historic landmarks in the city.