B'nai Jacob Synagogue - Ottumwa, Iowa - U.S. National Register of Historic Places on Waymarking.com

From Wikipedia:

"By the turn of the 20th century, Ottumwa had fewer than 50 Jewish families, immigrants from Germany and across eastern Europe. Most were 'in the junk and second-hand business', but there were also laborers, shoemakers, tailors and one prominent merchant. Some families were extremely observant, 'wearing two types of phylacteries', while others believed 'in no Judaism at all.' One local Jew had a personal Torah scroll and a private mikvah, but there was no organized community.

"In the early 1900s, many people called the area around the 300, 400 and 500 blocks of Main Street 'Jew Town' because the stores in the neighborhood were mostly owned by Jewish families, many of who lived above their stores. The B'Nai Jacob congregation was organized in 1898. In 1907, the congregation was located at 404 E. Main St., and had 15 members out of an estimated Jewish population of 150. The Hebrew school had 15 pupils and met once per week. By 1919, the Jewish population of Ottumwa had risen to 412 and the congregation had moved one block into the current building. The school still only had one teacher on staff, but there were 21 pupils and the school met daily. The B'nai Jacob congregation numbered around 250 in the 1930s and 1940s. The synagogue affiliated with the Conservative movement in the 1950s.

"The Jewish population of Ottumwa was 231 in 1951. By 1960, the Jewish population was estimated at 175, and by 1962, 150. For the next two decades, through 1983, the population estimate remained unchanged. By 2010, the congregation on a typical Saturday morning had shrunk to seven or so."

Shabbat morning services are still performed most Saturdays at 9 am.