One immediately arrived, but it was full.

When Jennings flatly refused to leave the whites-only trolley that she had already boarded, she was bodily ejected.

She sued the company for damages and won in 1855 — exactly 100 years before Rosa Parks rejected a Montgomery, Ala., bus driver’s order to give up her seat in the colored section for a white passenger after the space reserved for whites was filled.

In the mid-1950s, Parks was elevated to a civil rights heroine. Jennings was finally immortalized — in 2007, to a degree — after third- and fourth-grade students at P.S. 361 on the Lower East Side successfully lobbied to name a street corner in her honor.

Even in his revealing portrait of “Black Manhattan” (1930), James Weldon Johnson did not identify by name the “courageous colored woman, a teacher,” as he described Jennings, whose efforts led to the legal annulment of racially segregated mass transit in New York.

On July 16, 1854, Jennings and a friend, Sarah Adams, boarded the trolley at Pearl Street and today’s Park Row. They were late and rushing to get to the church, on East Sixth Street near the Bowery.

The reluctant conductor only agreed to let them ride — instead of waiting for a trolley that proclaimed “Colored People Allowed in This Car” — if no white passengers objected.

Jennings wrote, “I was a respectable person, born and raised in New York, did not know where he was born and that he was a good-for-nothing impudent fellow for insulting decent persons while on their way to church.”

Whether or not any rider voiced a complaint was unclear, but the conductor and Jennings scuffled. She resisted, clinging to a window frame, then to his coat. He enlisted the driver’s help, to no avail.

“I screamed, ‘Murder,’ with all my voice and my companion screamed out, ‘You will kill her. Don’t kill her,’ ” Jennings wrote.

“‘You shall sweat for this,’” she quoted the conductor as saying. Farther on, near what is today Canal Street, he spotted a police officer, who boarded the car and ousted Jennings. He shoved her onto the sidewalk, dirtying her dress and crushing her bonnet.

While Jennings’s encounter with the conductor was serendipitous, she had been primed, by temperament and family ties, for a confrontation over racial equality and to seek retribution.

Elizabeth Jennings was born in Manhattan in March of 1827 (although some records say 1830).

Her mother was Elizabeth (Cartwright) Jennings, whose own father had fought with the Continental Army. Young Elizabeth’s father, Thomas L. Jennings, was a prosperous tailor on Church Street and is said to have been the first black person to be awarded a patent in the United States, in 1821, for a method of dry cleaning clothes.

When Elizabeth was only 10 she delivered from memory a lecture titled “On the Improvement of the Mind,” according to a biography, “Streetcar to Justice” (2018) by Amy Hill Hearth.

When she finished public school, she wasn’t allowed to participate in commencement, so, in a separate ceremony, she received her diploma, which qualified her to teach in public school.

Her father, who had helped found the New York African Society for Mutual Relief, a charitable group for free blacks; enlisted his fellow abolitionists to publicize his daughter’s mistreatment and recruit a newly minted 26-year-old lawyer and future president, Chester A. Arthur, and his partners to sue the Third Avenue Railroad System, based in Brooklyn, for discrimination.

(In 1852, Arthur’s advocacy helped liberate slaves who were being transported from Virginia to Texas through New York.)

Frederick Douglass’s Paper, published in Rochester, and The New York Daily Tribune were among those that printed sympathetic accounts, relying largely on Jennings’s version of the altercation. (The New York Times apparently overlooked the case.)

On Feb. 22, 1855, Judge William Rockwell advised a jury in State Supreme Court that the company was required as a common carrier to convey all respectable passengers, including “colored persons, if sober, well-behaved, and free from disease” and that it was liable if they were excluded.

Jennings sought $500 in damages. The jury ruled in her favor, but apparently decided that amount was too much for a black person and instead awarded $225 (about equal to her annual salary teaching). The judge added 10 percent (for a total of about $7,000 in today’s dollars) plus costs.

“Railroads, steamboats, omnibuses, and ferry-boats will be admonished from this, as to the rights of respectable colored people,” The Tribune declared. “It is high time the rights of this class of citizens were ascertained, and that it should be known whether they are to be thrust from our public conveyances, while German or Irish women, with a quarter of mutton or a load of codfish, can be admitted.”

Jennings taught for 35 years, mostlyin black schools.

In 1860, she married Charles Graham. They had a son, Thomas, who was sickly and died when he was 1. His burial would take place during the Draft Riots by whites opposed to conscription during the Civil War, and since it was unsafe for blacks to be seen outdoors, Jennings and her husband had to sneak to their son’s graveside service at Cypress Hills Cemetery in Brooklyn, where the Rev. Morgan Dix of Trinity Church presided.

After the riots, in which dozens of blacks were killed, the couple fled the city. They settled in Eatonville, N.J., near Long Branch. Graham died in 1867. Jennings returned to Manhattan in 1871.

Jennings later taught at the Colored Grammar School, where the principal, Charles L. Reason, was a pioneering black educator who challenged school segregation.

In 1895, she founded what was described as the first kindergarten for black children, at her home, 237 West 41st Street, in Manhattan, where she died on June 5, 1901.