Mansfield Merriman was hired as chair of Lehigh's new civil engineering department in 1878. By 1881 he was also giving lectures in the mechanical engineering department as well. He graduated from the Sheffield scientific school of Yale University with a BS in Civil Engineering in 1871, and in 1873 entered the United States corps of engineers as assistant engineer. In 1875 he returned to Sheffield as instructor of civil engineering, and in 1876 received the degree of Ph.D. for advanced studies. In 1880 he became an acting assistant of the United States coast and geodetic survey, and for five years had charge of the primary triangulation of Pennsylvania. Professor Merriman was a member of the American society of civil engineers, the American philosophical society, and other scientific bodies in the United States and Europe. He published numerous textbooks throughout his career and is also an important inventor in the field of hydraulics.
The hydraulics lab at Lehigh University, the oldest one at any university in the United States, was constructed after a generous donation from Merriman.