Mary is the daughter of James Gaston and Susannah Reneau.  Her birth year can be calculated as 1813 from the 1840 Census Record. The 1840 Census Record also gives her birthplace as Pennsylvania. The name of her husband, John Rhodes is given in the Probate record of William Gaston.
The census record of 1830 and 1840 confirms birth. 
1830 Census Records of Green Township, Monroe County, Ohio. Contains enumeration of James and Susannah Gaston Household.
1840 Census Records of Green Township, Monroe County, Ohio. Contains enumeration of James and Susannah Gaston Household and the enumeration of George Gaston Household. Mary is named with her age and birthplace in the household of James Gaston and her birth year can be calculated from it.
Probate Record of William Gaston confirms name, family relationship and the name of her husband. 
Filed for petition 2 Feb. 1866: "Harris Gaston the plaintiff shows to the court that William Gaston departed this life on __ day of __ and at the time of his death he was owner in fee simple of the following tracts of land situated in Owen County, Indiana, NW 1/4 of Sec 35 T 11 N R 4 W. containing 37 acres and another beginning at NW corner of the NE 1/4 of sec 35 T 11 N R 4 W containing 84 acres except 37 acres set off for Lydia Gaston. Said defendants John Gaston, Mary Rhodes, June Bennett, Sarah Melick, and Ellenor Williams are brother and sister to William Gaston deceased. Defendants Ann and Levina Gaston are the daughters of George Gaston deceased who was a brother to William Gaston. Probate Record Owen County Indiana Vol 4-1 1 Jan 1866-1 May 1871
January 31, 1866 Probate record: "Ann Gaston, Levina Gaston, John Gaston, Mary Rhodes, John Rhodes, Joseph H. Bennett, Jane Bennett, Ellenor Williams and John B. Williams are nonresidents of the State of Indiana. Appraisal showed the lands were not susceptible of partitions and ordered to be sold. The described land sold for sum or $675 on May 4, 1871.” Probate Record Owen County Indiana Vol 4-1 1 Jan 1866-1 May 1871.
↑ Entered by Roger Gaston, Thursday, November 14, 2013.