1.  John Trotwood Moore, ed.  1923.  Tennessee, the Volunteer State, 1769-1923.  S.J. Clarke Publ., Chicago (online at GenealogyLibrary.com):

p. 903	PETITION OF WATAUGA ASSOCIATION TO BE ANNEXED TO NORTH CAROLINA ...dated July 5, 1776... The humbel petition of the inhabitants of the Washington District, including the River Wataugah, Nonachuckie, &c...
p. 905	David Crockett... Oldham Hightower... Frederick Vaughn... John Davis...

Our subject is the only Oldham HIGHTOWER old enough to have signed the Watauga Petition.

2.  Marjorie Hood Fischer.  1996.  Tennesseans before 1800, Washington County.  Frontier Press, Galveston, TX.  The book is an index, not the records themselves.  On p. 150:

Name	Record Type	Year	Pg
Hightower, Oldum	Tax List: Isbell's Dist.	1778	639

This is the only HIGHTOWER record in the book.

3.  Census Index:  U.S. Selected Counties, 1800 (Broderbund CD-312).  Please see my WARNING regarding use of this database (the numerical data have the genders switched). 

1800 Census

Hightower, Oldham

NC

Buncombe Co.

p. 713

01001-0010103

These data should read:

00101-01001-03

which indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	16-25	1774-1784	= Hardy (b. 1779)
1 male	45 or over	in or bef. 1755	= Oldham (b. 1744)
1 female	10-15	1784-1790	= Jane (b. 1786)
1 female	45 or over	in or bef. 1755	= Sarah (b. bef. 1750)
3 slaves	all ages	in or bef. 1800	= names unknown

Also in Buncombe Co.:  John's brother, Austin HIGHTOWER, Jr. 

4.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com):  about 40 files here refer to our subject, with about half calling him John Oldham and the other half calling him just Oldham.

5.  Email from Ruth Hightower Smith:  insists he is Oldham, not John Oldham.