Empty Envelopes posted to Martha "Mattie" Baird Nicholson (Kate's mother/ Blackmar's mother-in-law), 1863-1864; 1867; 1897-1900; 1903, Box: 1, Folder: 9. Personal Papers of Frank Blackmar, PP 53. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/252818 Accessed May 24, 2024.