On the evening of May 20, 1855, Meachum and a man known only as Isaac assisted eight or nine people flee across the Mississippi on the first step of what they hoped would be a journey to freedom from slavery.

An account published in the Missouri Republican on May 22, 1855, indicates that the party of freedom seekers that left the Missouri bank of the Mississippi "in a skiff, a short distance above Bissell´s Ferry" included "a man, belonging to Mr. McElroy, of this county, and a woman with two children, belonging to Mr. Henry Shaw, and also a negro man belonging to Mr. Thornton, livery stable keeper."

All of these freedom seekers were, according to the newspaper account, caught on the Illinois shore. "A negro belonging to Mr. Cohen, and one, the property of Sheriff Maddox," as well as "another negro man" escaped that night. Receipts in the Shaw archives at the Missouri Botanical Garden document the escape and capture of Esther that night, as well as her sale downriver to Vicksburg shortly after the event.

Although another newspaper article referred to Mrs. Meachum´s residence (revealed by census records to have been on the north side of Fourth Street between Spruce and Almond) as a "depot" on the Underground Railroad, existing sources document only the single event that took place during that night.

On May 24, 1855, the grand jury of the St. Louis Circuit Court indicted Meachum and Isaac on two counts each of having "enticed" people held in slavery to seek freedom in another state. The Circuit Court record book reveals that the prosecuting attorney soon declined to prosecute Isaac, but the case against Meachum continued. Although the outcome of her case is unknown because of the incompleteness of the record book itself, it appears unlikely that the jury convicted her of the "crime," a situation not uncommon in such cases within the St. Louis area.

A marker on St. Louis´ North Riverfront Bike Trail marks the "Mary Meachum Freedom Crossing," commemorating the event