Different spellings have been found for Theodor's last name, Larssen and Larsen. Nevertheless, Theodor Larssen first worked in Moorhead, Minnesota for O.E. Flaten as a retoucher in 1893.
In 1895 he was a retoucher for Hans T. Hanson. In November of that same year he went into business with Carl J. Reis, purchasing the studio at 67 Broadway from Gilbert E. Flaten. In October 1897, Reis and Larsen sold their studio to Jacob Skrivseth. From 1898-1899 he was working for O.E. Flaten again in Moorhead.
After 1899 Mr. Larsen can no longer be found in either the Fargo or Moorhead city directories.