In 1835, Oberlin College in Ohio determined that it would admit black students. A very few other colleges did at the time, but Oberlin was unique in that it chose to do so as an explicit matter of college policy. At Oberlin, and a few other places both before and after the Civil War, black and white students were allied first in the cause of emancipation, and then for civil rights. 

Yet following the end of Reconstruction, even once revolutionary campuses like Oberlin and Berea College in Kentucky began to have color lines drawn across them. As John Frederick Bell demonstrates in his new book, Degrees of Equality: Abolitionist Colleges and the Politics of Race, while blacks remained in the classroom at Oberlin and Berea, they were gradually discriminated against in every other aspect of college life. Given that these colleges had been established to shape not the mental so much as the moral community on its campus, this amounted to a counter revolution that overthrew the ideals upon which Oberlin and Berea College had been established.

John Frederick Bell  is Assistant Professor of History at Assumption University in Worcester, Massachusetts. Degrees of Equality is his first book. 

Erratum: At 34:30, John Chapin was named as the fundraiser for New York Central College; John Bell says he should have said William Chaplin. (About whom you can read here on Professor Wikipedia.)

For Further Investigation

In the course of asking "why" I mentioned my conversation with Doug Egerton on the decline and fall of the Adams family; and I should also note an even older conversation with Doug about the history of Reconstruction
The featured image is a late 19th century stereoscope of the campus of Oberlin College
Berea College, according to Professor Wikipedia; and Adam Harris,  "The Little College Where Tuition Is Free and Every Student Is Given a Job". The Atlantic (October 2018)
Nat Brandt, The Town That Started the Civil War: The True Story of the Community That Stood Up to Slavery–and Changed a Nation Forever
Kabria Baumgartner, In Pursuit of Knowledge: Black Women and Educational Activism in Antebellum America 
Ronald Butchart, Schooling the Freed People: Teaching, Learning ,and the Struggle for Black Freedom, 1861-1876
Christi Smith, Reparation & Reconciliation: The Rise and Fall of Integrated Higher Education
John Frederick Bell, “Early Black Collegians and the Fight for Full Inclusion” Black Perspectives (May 24, 2022)