Mary Louisa was born en route to the Salt Lake Valley while her family traveled with the Brigham Young Company in 1848. Her family consisted of her parents, Edwin Dilworth and Mary Wickersham, and her siblings, Franklin Benjamin and Rachel Emma. Mary Louisa was born on 5 July, while the company was camped at Goose Creek. Also in the company was her aunt and uncle, Samuel Amos and Catherine Elizabeth Mehring.
When the family made it to the Salt Lake Valley, they ate with her father's brother, John Mills Woolley, who had traveled to the Salt Lake Valley the year before with the Abraham O. Smoot/George B. Wallace Company in 1847, according to Rachel Emma Woolley Simmons’ Biography.