"The Mountain Men," per Teddy Roosevelt

From The Winning of the West, Vol. 3, by Theodore Roosevelt, published 1900, G.P. Putnam's Sons:

"Having reduced South Carolina to submission, the British commander [Major Patrick Ferguson] then threatened North Carolina; and Col. [Charles] McDowell, the commander of the whig militia in that district, sent across the mountains to the Holston men praying that they would come to his help. Though suffering continually from Indian ravages, and momentarily expecting a formidable inroad, they responded nobly to the call. Sevier remained to patrol the border and watch the Cherokees, while Isaac Shelby crossed the mountains with a couple of hundred mounted riflemen, early in July. The mountain men were joined by McDowell, with whom they found also a handful of Georgians and some South Carolinans; who when their States were subdued had fled northward, resolute to fight their oppressors to the last. The arrival of the mountain men put new life into the dispirited whigs." 

The Call for the Overmountain Men

From King's Mountain and Its Heroes, by Lyman Copeland Draper, published 1881, P.G. Thomson, page 84:

When Colonel [Charles] McDowell became convinced that Ferguson's movement to the north-western portion of South Carolina, threatened the invasion of the North Province also, he not only promptly raised what force he could from the sparsely populated settlements, on the heads of Catawba, Broad and Pacolet rivers, to take post in the enemy's front and watch his operations; but dispatched a messenger with this alarming intelligence to Colonels John Sevier and Isaac Shelby, on Watauga and Holston, those over-mountain regions, then a portion of North Carolina, but now of East Tennessee; urging those noted border leaders to bring to his aid all the riflemen they could, and as soon as possible.
Sevier, unable to leave his frontier exposed to the inroads of the Cherokees, responded at once to the appeal, by sending a part of his regiment under Major Charles Robertson; and Shelby, being more remote, and having been absent on a surveying tour, was a few days later, but joined McDowell, at the head of two hundred mounted riflemen, about the twenty-fifth of July, at his camp near the Cherokee Ford of Broad river.

"... the transmontane men..."

From History of the McDowells and Connections, by John Hugh McDowell, pub. 1918, C. B. Johnston, pp. 234-235:

On the 29th of August, 1780, Colonel Ferguson moved into Troy (now Rutherford County) and camped, first at Gilberttown, three miles north of Rutherfordton, with the purpose of capturing Charles McDowell and destroying his command, and ultimately crossing into Washington and Sullivan counties (now Tennessee) and dealing with Shelby and Sevier of the Watauga settlement. Ferguson left Gilberttown with a detachment in search of Charles McDowell, but McDowell laid in ambush at Bedford Hill, on Crane [sic, Cane] Creek, and fired upon his forces while crossing the creek at Cowan's Ford. Major Dunlap was wounded and Ferguson was forced to retire to Gilberttown.
After this affair, Charles McDowell retreated across the mountains to warn Shelby and Sevier of the threatened desolation of their country, and to invite their co-operation in an attack on Ferguson. It was agreed that the transmontane men should be gathered as expeditiously as possible, while McDowell should send messengers to Colonels Cleveland and Hernando, of Wilkes County, and Major Joseph Winston, of Surrey. The energies of Shelby, of Sullivan and Sevier, of Washington County, N. C., then embracing the present State of Tennessee, were quickened by the message which Ferguson had released a prisoner to convey, to the effect that he would soon cross the mountains, hang the leaders and lay that country waste with fire and sword.
The clans were summoned to meet at Quaker Meadows on the 30th of September, 1780. Meantime Charles McDowell returned to watch Ferguson, protect cattle by assailing foraging parties, and give information to Shelby and Sevier of Ferguson's movements.
Rev. Samuel Doak invoked the blessings of God upon the Watauga men, as they left for King's Mountain to meet Ferguson, whose blasphemous boast had been that God Almighty could not drive him from his position. Those trustful old Scotchmen afterwards believed in their hearts that the hand of God was in the movement which cost him his life and destroyed his force.