Facts and Events
There are 5 vital records available on MyHeritage for Joshua Walker, including birth records, marriage records, and death records. Vital records are historical records that are typically recorded around the actual time of the event, which means they are likely accurate. Vital records include information like the event date and place, and the person's occupation and residence. Vital records also often include information about the person's relatives. For example, birth and marriage records include names of parents and divorce records list the names of children.
Elizabeth apparently died by 1800, as in that year Joshua remarried Amy Williams. His pension application documents this marriage as occurring in Grayson County. 
The child lists for Joshua by his two wives are somewhat confused. There are relatively few researchers working on this family, and the child lists provided by the different researchers are not in agreement. In particular, DOB's for different persons believed to be the children of Joshua, vary considerably, such that they could be the children of either Elizabeth or Amy. Additional work is needed to resolve these discrepancies.
Sometime after their marriage Joshua and Amy settled near Bull's Gap, in Hawkins County Tn, where they remained for the remainder of their lives. Joshua's pension records indicate that he died in 1840.
Information from “Virginia/West Virginia Genealogical Data from Revolutionary War Pension and Bounty Land Warrant Records”, Vol. 6, compiled by Patrick G. Wardell, Lt. Col. U.S. Army Ret. :
Walker, Joshua - born 15 February 1757 in Loudoun County, Virginia; entered service 1776 in Washington County, Virginia regiment against Cherokee indians; granted Pension 1834 in Hawkins County, Tennessee; died there 1/16/1840; married 9/17/1800 to Amy Williams, Grayson County, Virginia, by Baptist minister George Keith, soldier then known as Samuel Jones alias Joshua Walker, per certificate 1856 by that County court clerk John Dickenson, & County Justice of the Peace Creed Nuckolls; widow granted Pension age 76 in Hawkins County, Tennessee, 1856; had 11 children of which eldest would now be abt. age 55, if living & youngest now age 32, Henry Williams made affidavit then in Hawkins County, Tennessee, he attended soldier's wedding; Claiborne Walker age 56 & John Walker age 48 (both no kinship given) made affidavit 1856 in Hawkins County, Tennessee, that they were at house of soldier & wife on day they moved to there & they were neighbors to them; widow's Pension restored at age 90 where she had resided since 1861; her attorney in 1848 was James H. Walker (no Kinship Given) of Bulls Gap, Tennessee; query letter in file 1918 from Clara Walker, Morristown, Tennessee; query letter in file 1918 from Thomas S. Walker, Greenville, Tennessee. F-W8301, R24758.