Good morning on this cooler Thursday.

Rosa Parks has been called “the first lady of civil rights.”

But a century before Ms. Parks refused to give up her bus seat in Montgomery, Ala., a young black schoolteacher took a similar stand in New York that led to the desegregation of our city’s public transit system.

It might never have happened, but she was running late.

On a sweltering Sunday morning in the summer of 1854, Elizabeth Jennings was on her way to play the organ at the First Colored American Congregational Church on Sixth Street in Lower Manhattan.

In a hurry, she hailed a horse-drawn streetcar at the corner of Pearl and what was then called Chatham Street, according to her account.

When Ms. Jennings tried to hop on, the conductor stopped her and told her to wait for a car with her “people in it.”