According to an online tree, William F. Holmgreen was born 28 Jan 1842 in Tromsø, Norway, and his wife, Helga Eriksen, was born 9 May 1854 in Telemark, Norway.
This tree shows Thomas Freddmont Holmgreen as their son.
This appears to be the correct family. Helga was born ca. 1854 - 1856. Since she arrived in the US in 1862 (according to the 1900 census), she must have arrived with her parents. I think her father was named either Tollef Eriksen or Erik Tollefsen.