Conversation so far:
What is Harold Innis' dirt research?
Harold Innis traveled the country himself gathering masses of firsthand information and accumulating what he called dirt experience.
What kind of information was Harold Innis gathering on his dirt experience?
During his travels, Harold Innis supplemented his fur research by gathering information on other staple products such as lumber, pulp and paper, minerals, grain and fish.
When did Harold Innis start his dirt experience travels where Innis supplemented his fur research by gathering information on other staple products such as lumber, pulp and paper, minerals, grain and fish?
Harold Innis travelled extensively beginning in the summer of 1924.

Question: Where did he travel?
Self-contained rewrite: Where did Harold Innis travel extensively beginning in the summer of 1924?