The Castle is a private residence that has distinctive Gothic Revival architecture and great historic significance. Located at 220 5th Street, Marysville, it was built in 1851 and owned first by José Manuel Ramirez and later by Charles Eamer Sexey (who never actually lived in it) and W. T. Ellis, Jr. It was built with wooden beams imported from Ramirez' home country of Chile and brick plastered over and scored to resemble stonework. The interior and exterior walls on the first floor are all two and a half feet thick.