This grave is in the Mound City National Cemetery.

Mound City was the home of a naval shipyard where several of the Union ironclad gunboats were built.
It was also the location of a large hospital complex.

More information on Mound City and the cemetery can be found here:
https://www.nps.gov/nr/travel/national_cemeteries/illinois/mound_city_national_cemetery.html#:~:text=Although%20the%20Mound%20City%20area,80%20vessels%E2%80%94was%20located%20here.