In the 17th century the Scots formed a separate nation connected with England only because the two peoples shared the same monarch. Varying English dialects were spoken in the Lowlands; the Highlanders brought their Gaelic to America. Most of the emigrant Scots were Presbyterian Lowlanders who had settled in northern Ireland when James I began his "Great Plantation" to put down rebellion among chieftains in the Ulster area. Persecuted by Cromwell, and later by William and Mary after the battle of Boyne, the native Irish were relegated to the backward mountainous regions with the poorest, least arable land.
The Scotch-Irish, as the Ulster Scots came to be known, fared only a little better than the supplanted Irish. They were hard hit by the WoolenAct of 1699, which made it illegal for their weavers to export their cloth to any foreign country. Furthermore, an act of 1704 disenfranchised all who would not conform to the established Angelican Church. Disillusioned and embittered, a steady stream embarked for America; some 200,000 Scots had left Ulster up to 1776. A substantial number of the Scotch-Irish settled in the back country of Pennsylvania. Many moved down the Appalachian valleys into the Carolinas, where they settled the frontier wilderness, often as squatters, and took over a considerable share of the Indian trade.
Highlanders began coming to America after the unsucessful Scottish rebellions of 1715 and 1745-1746, which attempted to restore the Stuarts to the Engilsh throne. Some came as fugitives, most as exiles who swore allegiance to the Hanoverian kings of England as the price of their freedom. Most Highlanders gravitated to communities made up of their countrymen on the farming frontier.
The Scotch-Irish stood in the forefront of rebellion, for they , along with the Celtic Irish, aborred English rule.
From The National Geographic:
After the Battle of Culloden the English ruthlessly suppressed Highland culture, outlawing the carrying of sheilds and swords, the wearing of kilts, and even playing of bagpipes. In 1822 the Highlands were so thoroughly pacified that on his first state visit to Edinburgh King George IV allowed Sir Walter Scott to swathe his royal rotundity in Stuart tartan.
Clan: The word originally meant, in Gaelic, offspring or descendants, family or tribe. Originally a family unit, the clan became the basic political, economic, and social unit of the Scottish Highlands until the political oppression of 1745. Each clan has it's own tartan which was worn in a kilt or scarf. They were fiercly loyal to the family group and are quick to avenge any wrongs done to their fellows, as well as defending the area they considered home territory.
Sept: A family not having the name of the clan, but associated with the clan and entitled to wear it's tartan.