What were the causes for English colonial expansion into the West during the mid-1700s?
If we mean the American, or Trans-Appalachian West, then the reasons were fairly simple. American colonists desired more cheap land so that they could become independent landowners. This was the driving force behind westward expansion ever since the establishment of colonies along the North American coasts, and was a source of constant tension between British colonists and Native Americans. In the mid-eighteenth century, the main destination for settlers was the Piedmont of Virginia and the Carolinas and even as far south as Georgia. Settlers, mostly Scots-Irish, made their way down the so-called "Great Wagon Trail" from Pennsylvania into the region, where cheap land was to be had. In a little over a decade, settlers were already moving into the Ohio River Valley and Kentucky, defying a proclamation from King George III that lands west of the Appalachians were not to be settled. So expansion into the West was more the result of the desires of ordinary colonists (and wealthy land speculators) to gain cheap land than a concerted effort on the part of the British crown to colonize the region. In fact, the Crown sought to limit these settlements.