Benjamin Provoost's Straightedge
It may not look like it has anything to do with railroad history, but this straightedge was one of many surveying tools used by Benjamin Provoost, who was a civil engineer and served as division engineer of the Illinois Central in the 1850s in and around Dubuque.
Provoost helped build the Illinois Central Railroad and oversaw the route that ran from Eldena, Ill. to Dubuque, Iowa. In 1954, he was promoted to chief engineer of Dubuque & Pacific railroad. Provoost later became the director of the Second National Bank in Dubuque.