Complex sentence: Some of the best-known names in Minnesota history (Henry Hastings Sibley, Ramsey Crooks) were active and running a fur trading company in the area and while in their service Joseph Rolette rebuilt a trading post at Pembina.
Split into simpler sentences: Some of the best-known names in Minnesota history (Henry Hastings Sibley and Ramsey Crooks) were active and running a fur trading company in the area. While in their service Joseph Rolette rebuilt a trading post at Pembina.