[2]: 6  During this time he spent about a year in Great Britain, where he apprenticed with Sir John James Burnet in Glasgow and then with Thomas Edward Collcutt in London, and then returned to Montreal.

[3] Larson returned to Canada in January 1919 before making his home in Hanover, New Hampshire, where he was architect in residence at the Ivy League school Dartmouth College from 1919 to 1947.

[4][5][6] According to scholar Rod Andrew Miller, Larson's 1928 Baker Memorial Library at Dartmouth "garnered much attention"; Miller quoted a June 1930 letter to Larson from Princeton University librarian James T. Gerould that said: "The longer I study the Dartmouth building the more thoroughly convinced I am that, in its adaptation to purpose, it is the best building we have in the country.

[14] He completed a full design for the University of Louisville, but the project was quashed in part due to World War II.

[2]: 8 For more than fifty years, Jens Fredrick Larson designed almost exclusively in Colonial Revival style before and during the period when the extremely different mid-century modern architecture was rising in popularity.