Parker pursued engineering with the same focus he had brought to law.

He studied at Rensselaer Polytechnic Institute, one of the preeminent engineering schools in the country, and he developed the technical skills that would define his professional life for the next two decades.

He worked on canal and harbor projects in New York, gaining practical experience in civil engineering and construction management.

He was skilled, reliable, and capable of overseeing complex projects, and he built a reputation in his field.

In 1857, Parker moved to Galena, Illinois, to serve as superintendent of construction for a federal customs house and other government buildings.