He attended the public schools of Wauwatosa and Wayland Academy, Beaver Dam, Wisconsin.
In 1867 he entered the employ of the Chicago, Milwaukee & St. Paul Railroad, rising from clerk and brakeman to division superintendent.
[2][1][3] In 1875, he married Sara Virginia Smith, by whom he had two sons, Enoch William and Russell Sage Underwood.
[4][note 1] In 1886 Underwood was named general superintendent of the Minneapolis and Pacific Railway.
[3] When Hill had become a major shareholder in the Baltimore & Ohio Railroad, he secured the appointment of Underwood as vice president and general manager in 1899.
[6] During his tenure he made good use of limited financial resources to rebuild the long-troubled Erie as a first-class railroad, especially as a freight carrier.