The tall pyramidal building might be a shot tower, which was a place where lead shot, as for shotguns, was made. The basic idea was to release droplets of molten lead from a height. They would solidify into spherical shape while in free fall, then land in a tub of water. They'd be removed from the tub and sorted for size and checked for roundness before being packed into canvas sacks. There were shot towers in many US cities. (Shorpy has an early view of Manhattan which shows one.)

What is the use of the dark, pyramidal building in the background? I don't see any chimney on the top, so it doesn't seem to be a heating source. It has a window about halfway up. Sure has me wondering.

This building is not incorporated in the current Michigan Masonic Home building. This building is located near downtown Alma on State Street. Parts of this building still stand but not all of it. Most of it was torn down after the Masons moved out.

The current facility was built in 1929 on Wright Avenue.

http://www.michmarkers.com/default?page=S0567

There are a lot of erroneous articles thanks to a local "historian" who did not do his research very well.

By the first decade of the 20th century, Ammi Wright had seen enough. His once spiffy hotel, built right next to his own handsome house in Alma, just wasn't drawing them in anymore. "Taking the waters" was having a rough time competing with the advances of medical science. But he got a break. The Masonic Home for the elderly in Grand Rapids burned down in 1910 and the fraternal group was on the hunt for new digs. Wright offered his sanitarium for $60k along with 80 acres. The Masons balked. Wright lowered his offer to free, please just take the damn place. Offer accepted. The original structure pictured is still there, in a way. Over the years Michigan Masonic added a new main building and others, repurposing most of the pieces from the 1885 edifice. Waste not, want not.