Thomas Peter Thorvald Kristian Ferdinand Mortensen was born in Skaarup, Skanderborg, Denmark, on 16 August 1882, to Jens Carl Martinus Mortensen and Maren Therkildsen Thyboe. The youngest of six siblings, he was baptized in Fruering Church on 26 December 1882. Besides his baptismal record, other records used for validation of his age include the 1890 and 1901 census enumerations in Denmark, and church confirmation in 1896.
In 1903, he migrated to the United States, and lived in various areas and worked in various trades including as a milkman and in a can factory. In Denmark, Mortensen had worked as a farmhand and apprenticed as a tailor. He apparently was married, though only briefly and never had children. In 1978, he rode his tricycle to the Aldersly Retirement Community in San Rafael, boldly telling the staff that he was Danish, and that he was there to stay. Mortensen lived there for his final 20 years.
Mortensen enjoyed an occasional cigar, and, very unusually for a supercentenarian, was known to show a bit of feistiness even in his final years. In August 1997, for instance, he expected to get the Guinness “oldest person” title, but on 14 August 1997, Guinness named Marie-Louise Meilleur of Canada, age 116, the “world’s oldest person”. Mortensen, angered, said they “just did that to spoil my birthday” (he turned 115 only two days after). Later, however, when he found out that fellow American Sarah Knauss was older too (116 as well), he said “c’est la vie” (translated: “that is life”). Mortensen could have been given the title of “oldest living man”, however, but Guinness did not officially implement that category until mid-2000.
Mortensen died in San Rafael, California, USA, on 25 April 1998.