Barack Obama ’83, My Columbia College Roommate
By Phil Boerner ’84
https://www.college.columbia.edu/cct/archive/jan_feb09/alumni_corner
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https://en.wikipedia.org/wiki/Wayne_Allyn_Root
Root attended the Thornton-Donovan School in New Rochelle, N.Y.,[5] and was a member of the class of ‘83 at Columbia University, studying pre-law and political science.
IF Columbia College and Columbia University are two distinctly separate institutions, there’s your answer.
They are not physically or administratively distinctive, same campus and same school with different divisions, one of which is Columbia College. Still, the campus is fairly large and the likelihood of knowing someone is dependent on whether you are in the same classes or dining hall or dorm.