The professor in History 3535 said some things that professors do not usually say during a history class, among them, “Move over — we have to let the cab through.” It was nearly 2 a.m., hardly the normal time to be lecturing 200 students.

Nor was the professor, Kenneth T. Jackson of Columbia University, standing behind a lectern in a lecture hall with comfortable seats in which sleepy students could doze off. He was standing at the corner of Fifth Avenue and Washington Square North, a little more than six miles from the campus. And the students were wide awake.

This session of History 3535 — “History of the City of New York,” as it is listed in the university’s official directory of courses — was unusual, and deliberately so. It was an all-night bicycle ride. Professor Jackson, on a cherished fire-engine-red Trek, led the way through Manhattan and across the Brooklyn Bridge in the early hours of Friday.

The ride was also a Columbia tradition, because Professor Jackson has led one every couple of years since the mid-1970s. He is now 75, and some students worried that he might not lead another. He said this one was “probably not” his last. “But if I do it again,” he said, “I may have one of those hansom people pedal me around the way they do in Times Square.”