This is in Greenstreet, Saskatchewan on July 28, 2018. A rail line used to run through here. People live in Greenstreet, there just is not that many of them.
There once was a grain elevator to go with the annex. The annex was to increase storage capacity for the elevator. The elevator would have sat on the concrete pad at the end. I have never seen an annex without an elevator.
To see an example of an elevator and annex visit this page.