Simpson was in the Columbia District in 1841.
"He set off from London on May 3, 1841, and was traveling fifty miles a day on horseback and up to one hundred miles a day by canoe. Along the way, in the Red Deer Hills of present day Alberta, Simpson caught up with the Sinclair expedition of settlers he had ordered to the Columbia District. Simpson told Sinclair that instructions had been left at Fort Edmonton as to how he was to cross the Rockies. Simpson wrote in his diary, "Each family had two or three carts, together with bands of horses, cattle and dogs. As they marched in single file their cavalcade extended above a mile long. The emigrants were all healthy and happy; living with the greatest abundance and enjoying the journey with great relish.""
All I can find is that McLoughlin and Simpson disagreed about having ships and ports along the coast.
"In 1841 Dr. John McLoughlin was knighted by Queen Victoria at Buckingham Palace. However, by 1841, Simpson and McLoughlin were in complete disagreement about how the district should be run. Simpson and McLoughlin disagreed over the matter of establishing posts on the coasts and keeping ships in port. Dr. John did not want ships because of the unpredictability of ships crews and their harassment and problems with Indians. McLoughlin did not like Simpson's callous handling of his son's murder. Also, Simpson did not like the Yerba Buena idea, especially since it was sure to be US territory, south of the Columbia. At this time, his superiors realized the many settlers coming might result with the fort being on US soil. So McLoughlin was ordered to move everything to Vancouver Island and build a new fort there. This fort was called Adelaide, which eventually became the city of Victoria."