Commonly called a “Crossing Gate House”, "Crossing Shanty" or "Watch Box", these were placed at grade crossings until automatic crossing gates became common toward the middle of the 20th Century. Crossing Watchmen operated the manual Crossing Gates and used a Stop Sign to control traffic at the crossing. 

Watchmen were also required to inspect passing trains for defects, report engineers who failed to properly sound the whistle or ring the bell at the crossing, and were expected to keep the crossing area clear of snow or other debris that might interfere with safe operation. 

The structures were usually placed near the tracks so the flagman could relax and keep warm in the winter. Since little physical labor was required, the job often was assigned to employees on light duty from injury or otherwise disabled.