Immaculate Conception Roman Catholic Church has a rich history stretching back to 1840, making it one of the oldest parishes in Missouri, and probably west of the Mississippi. The current church dates from 1895. Franciscan sisters provided for the education in the parish school, which dates to 1857. Some of the earliest buildings were log cabins.
While I was looking at the church, I also spotted this really nice telecommunications tower, sticking up above the trees.
Another landmark in Arnold is the water tower; apparently many years ago there was some controversy when the local water district painted over the name “Arnold” and replaced it with “Public Water Dist. 1.” Apparently there is a compromise now with the return of the name of the city.