St. Ambrose Cathedral is a historic Catholic church built in 1891. It is a fine example of Romanesque Revival architecture and features a tower that stands 120 feet tall. Designed by architect James Egan, the church is the third building for the St. Ambrose congregation, which was the first Catholic congregation in the city. The building also features stained glass windows depicting the arrival of Catholicism in Iowa and in the U.S.; this is unusual for Catholic Church as stained glass windows typically portray biblical themes. The church was added to the National Register of Historic Places in 1979.
Catholic missionaries arrived in Des Moines in the early 1850s. The first mass took place in a log hut in Fort Des Moines in 1851. Then in 1856, the first church building, a small 40 by 24-foot wooden structure, was erected. The second church, a stone building, was built in 1865. As the congregation grew in the coming decades, the need for a larger building became apparent. The current structure was built in 1891 and was later declared a cathedral when the Diocese of Des Moines was founded in 1911.