Contemporary scholarship does challenge some of what he writes of, such as his chapters on the Underground Railroad, particularly in terms of numbers of slaves making their way toward the North Star, and the stations. So it's unfortunate this work was written before Henry Adams, Theodore Roosevelt and others began teaching the methods of history as a discipline (which at least Henry Adams imbibed during his long stays in Europe from practioners there), so there are no sources cited, no footnotes. But the Abolitionist passion breathes out of every sentence, nor is there any reason to doubt the accounts he provides of individual white people who did help escaping slaves in all the variety of ways open to them. For one thing, as so much of this action took place across what was then still called the Northern Reserve -- western New York and northern Ohio -- there are many local archives that contain the newspapers, memoirs and other documentation for such events at Case University and other institutions.
Henry Wilson was elected Vice President of the U.S. on President Ulysses S. Grant's ticket. He served as VP until he died, in harness.
Wilson is a fascinating figure, a life-long Abolitionist from Massachusetts, born in New Hampshire. He was one of the Radical Abolitionists along with the more famous Thaddeus Stevens. Like Stevens the winds of scandal blew about Wilson, though of different sorts of scandal than Stevens's. Much information on Wilson can be found here.
It is good to remember the Aboltiionists, particularly when the Lost Causers who cling to the revisionism of the Civil War insist the war wasn't about slavery, and that the North, as racist as the South, didn't care about slavery. My response to this supposedly killing argument is, "Remember the Abolitionists." And nothing created Abolitionists out of northern racists faster than the Fugitive Slave Act. Wilson documents this consequence in granular detail.
Fortunately, perhaps, Wilson died, before the Corrupt Bargain of 1876 that traded the end of Reconstruction for Hayes's election.