[1][2] At a young age, his family moved to Washington, D.C..[3] In early 1847, Wood enlisted in Cumberland, Maryland, with the 3rd Regular Cavalry in the Mexican–American War, under General Samuel Hamilton Walker.

[1] In the 1850s, Wood was called as an "expert witness" against Cyrus McCormick in the patent case for the mechanical reaper.

[3] In the years leading up to the Civil War, Wood was a conductor on the Underground Railroad, helping hundreds of former slaves escape to New England and Canada.

[2][3] Secretary Stanton asked Wood to help Lafayette C. Baker investigate recruiting scandals in New York City.

[3] After the assassination of Abraham Lincoln, Wood was summoned back to Washington by an urgent telegram from Edwin Stanton to assist in the investigation.

[2] Following this, he was sworn in on July 5, 1865, by Secretary of the Treasury Hugh McCulloch to head the newly formed Secret Service.

[2][3] During his time as head of the Secret Service, he captured Charles Ulrich, a counterfeiter based in Cincinnati, Ohio.

[1][2] He died of Bright's disease on March 20, 1903, at Soldiers' Home in Washington, D.C. At the time of his death, he was writing his memoirs.