Complex sentence: In 1810 Mackay, along with several other retired NWC personnel such as Donald McKenzie and Duncan McDougall, signed a preliminary agreement with the American businessman John Jacob Astor, who intended to establish a new fur trading company operating in the Columbia River region.
Split into simpler sentences: In 1810 Mackay, along with several other retired NWC personnel, such as Donald McKenzie and Duncan McDougall, signed a preliminary agreement with the American businessman John Jacob Astor. Astor intended to establish a new fur trading company to operate in the Columbia River region.