It's the pump house for the irrigation system that runs throughout the cemetery. It's also been used to store hay for the cemetery horses (who had a separate barn) and as a sawmill to cut up trees for firewood. There are three wells. Water used to go to a water tower and then throughout the park by gravity. But the water tower fell apart and now they use electric pumps which cause them no end of trouble.
I've put the photos together in a set with more explanation here
www.flickr.com/photos/yooperann/sets/72157616745149303/ 