HiEd: You are on target!
The Library of Virginia ,Richmond, (has a web site)
The City of Alexandria,http://ci.alexandria.va.us/oha/lyceum/ly-historic.html
The Virginia Historical Society,www.vahistorical.org
The Library of Congress, www.loc.gov
Please remember I am researching the Mecklenburg line and not the "John the immigrant line".
The Hon, Mark Alexander wrote a letter to the Hon, Hugh Blair Grigsby,of Charlotte Co.,Va. on July 2,1876, giving a brief history of his own family in his own words.
I have other letters and papers to document that line to their landing at "The Head of the Elk", in the years between 1685 and 1715. The Elk River is at Elkton MD., where they landed and separated after leaving Ireland and Scotland.