added 1940 census source below, should be enough to kickstart more research
Sources
↑ "United States Social Security Death Index," database, FamilySearch (https://familysearch.org/ark:/61903/1:1:J2WF-H5Q : 8 January 2021), Thomas L Mark, 24 Jan 2000; citing U.S. Social Security Administration, Death Master File, database (Alexandria, Virginia: National Technical Information Service, ongoing).
1940 US Census - "United States Census, 1940," database with images, FamilySearch (https://www.familysearch.org/ark:/61903/1:1:KQD9-V3K : 7 January 2021), Thomas Mark in household of Cecil Mark, Smithfield Township, Huntingdon, Pennsylvania, United States; citing enumeration district (ED) 31-50, sheet 11B, line 49, family 222, Sixteenth Census of the United States, 1940, NARA digital publication T627. Records of the Bureau of the Census, 1790 - 2007, RG 29. Washington, D.C.: National Archives and Records Administration, 2012, roll 3515.
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This isn't my Mark family but a notice of edits brought me here. Research notes in profile, appears to be Swiss Mennonite, 'Merki' family arrives in colonial America c1735, name variant Merck, Mark appears late 1700s ...per notes at Ancestry.