I am also currently scouring the 1830 Census in Missouri page by page (it is so unfortunate the indexes are often not complete or incorrect) trying to find a clue to Margaret's Garvin spouse.
Thank you so much for the info on Margaret's land purchase.Margaret and Simeon's marriage was the second for both of them, so it is possible Margaret's listing her last name as Garvin was in the interest of her children Mary Reed, John T., Elizabeth Young, Frances I., and Benjamin D. Garvin, to keep the family name going.Also, Simeon already had at least 2 children from his first wife Mary "Polly" Woods, one being named George H. Frost b. about 1825 and the other Mary Frost b. about 1828, so maybe also Margaret didn't want Simeon's children to inherit the land.
Info on Simeon Frost Father: Simeon Frostb. About 1761Of Jessamine County, Kentuckym. About 1782Jessamine County, Kentucky Mother: Martha Mrs. Frostb. About 1762Of Jessamine County, Kentucky m. 1809 Jessamine County, Kentucky to Spouse: Mary or Polly Woods b. 1790 in Kentucky, death 1839, Crawford County, Missouri, Parents: Ahijah & Mary Woods
Simeon died on an oxen wagon train 10 miles west of Independence, MO while on his way to California in 1849 or 1850.