Jasper Vandiver and Fleckner J. Smith | Marriage Record "Missouri, County Marriage, Naturalization, and Court Records, 1800-1991," database with images, FamilySearch (https://familysearch.org/ark:/61903/3:1:3QS7-L989-M72S?cc=2060668&wc=ZMYV-T38%3A1583614202%2C1583614403 : 26 April 2019), Knox > Marriage records 1845-1881 vol 1 > image 151 of 330; Missouri State Archives, Jefferson City.
John Bright Shiplist The listing of James Smith II's family when they traveled by ship to the United States.
The youngest child to sail was indeed Martha - although the ship list states Matthew.