Alexander Montgomery, of Amherst County, Virginia and Orange County, North Carolina
Facts and Events
Some genealogists identify Alexander Montgomery's father as John Montgomerie of Argyle, Scotland, who died in Monmouth County, NJ about 1721. Alexander himself may have been born in Argyle, as some genealogists indicate that he entered America through New York, presumably immigrating with his parents. Others show him first in New Castle County Delaware, and give that area as the place of birth for his children. These various views may all be true, with him migrating first to America through New York, moving south to New Jersey with his parents, and then moving on to Delaware. These views may also be unfounded, as direct evidence for them is not commonly reported. Direct evidence for his birth in Scotland, immigration through New York, then New Jersey, and/or living in Delaware is needed. The current working assumption is that he probably settled initially in Delaware, eventually moving westward through Pennsylvania, and down the Valley of Virginia, before crossing eastward across the Blue Ridge to settle near Rockfish Gap, in what was then Albemarle County, and is now Amherst County. While an unusual migratory path, others such as Person:Michael Woods (1), settled in Albemarle about 1733 are known to have followed very similar path. Woods researchers believe that those following this path were part of a group of Scot-Irish settlers who settled initially on/near the Nottingham Lots of Old Chester, moved westward to the Cumberland Valley, then followed the valley south into Virginia, before turning east near Staunton to settle on the eastern side of the Blue Ridge in Albemarle/Amherst/Bedford Counties.
Alexander Montgomery of Orange County NC is commonly described as coming there from Amherst County, VA. This belief is at least partially substantiated by the fact that he left a bequest to one of his sons for property in Rockfish Gap, Amherst County. 
After his death one of his children deeded land they inherited from him, back to his wife, identified only as "Mary". From an undocumented (see caveats in Note 2, below) source:
Alexander 2nd received 170 acres of land in Orange County, North Carolina, from his father’s will. On 3 Jun. 1769 Alexander and wife Martha deeded this land to his father’s widow, Mary Montgomery.
The documentation for this transfer describes her as Alexander's widow, not the mother of this particular child. It may be that Mary was his second wife, and may not have been the mother of any of his children. Some give his wife as Anna Sutherland b: 1705 in Isle Of Islay, Argyll, Scotland. The basis for this is unknown.
In general, it seems safe to accept the view that Alexander of Orange County came there from Rockfish Gap in Amherst County, VA, and almost certainly came to Orange County in the company of a number of other families (e.g., Dobbins, Maxwell) who also seem to have ties in that general area.
Alexander made his will in 27 Jul 1767 in Orange County, NC. It was proven the following Apr 1768. His date of deathis sometimes given as "1767/68", which might suggest an "Old Style/New Style" date, implying that that he died between January and March of 1768  It may also be that the use of "1767/68" simply reflects that we don't know his exact date of death. (probably the latter as the Gregorian calender was adopted in 1752--Scot 13:14, 22 February 2012 (EST))
At least one child of Alexander (John) remained in Amherst County, dying there in 1784. Some of John (93)'s children remained in Amherst County, but others moved to Kentucky, and beyond. Two of Alexander's children [Mary (52) and William (22)] moved on to Kentucky. Alexander (27) moved to Southwest Virginia, settling in the Castle's Woods area, near his fatherinlaw John Walker (81) of the Wigton Walker line. Nothing is known of the children of daughter Elizabeth (47) and her husband William Maxwell. William is presumed to be kin, probably son of, Bazaleel Maxwell (possibly Person:Bazaleel Maxwell (1)), who lived in the same general area as Alexander (9)'s kinsmen. If Bazaleel of Orange County is indeed Bazaleel (1), then he left North Carolina at some point to settle in Garrard County, Kentucky. It may be that son William Maxwell went there as well.
Father: John MONTGOMERIE b: 28 MAY 1668 in Dundonald, Ayrshire Scotland
The following children are listed as a first marriage and are included in Alexander's will Children:
The following children were listed as specific to Mary as a second marriage, but are not listed in Alexander's will While there='s no question that Mary was Alexander's wife at the time of his death, what is the evidence that the children he did list were by a previous marriage? Why are these children excluded from his will? Marriage 2 Mary Children
Source:"Branches of Montgomery and Longs by Isla Montgomery, crediting the research of Ruth Chambers Little of Tappannoch, VA Intermediate Source:Mounet.com
With some typo corrections:
There is much speculation concerning our oldest know Montgomery ancestor (Alexander ca. 1700-1768). Some believe he immigrated from Ireland with the Barnetts with whom some of the Montgomerys internarried. Isla believes that Alaxander son of John was born in Ireland. In the "Bicentennial History of Lee County Virginia" one descendant states that Alexander landed in New Castle, Delware but there appears no evidence to support this.