Some secondary sources say Elizabeth was the niece of Jefferson DAVIS, President of the Confederate States of America.  To be Jefferson's niece, Elizabeth's father had to be Jefferson's brother.  Benjamin DAVIS, brother of Jefferson, was born in 1787/8 in Georgia, not in 1794/5 in Tennessee, and he married Aurelia SMITH (ca. 1824), not Lavina PERRY.  Benjamin & Aurelia (SMITH) DAVIS, had just one child, Mary Ann DAVIS (1825-1828), who did not survive.  None of Jefferson DAVIS's other brothers had a daughter, Elizabeth, either, so this Elizabeth DAVIS is definitely not a niece of Jefferson DAVIS. 

2.  Luke Lee CUPP, b. 1832/3, Schuyler [now Brown] Co., IL; d. 15 Jan 1911, La Plata, Macon Co., MO; m1. 13 Apr 1852, Brown Co., IL, Permelia A. TAYLOR; m2. 28 Sep 1854, Brown Co., IL, Harriet Jane UPCHURCH

3.  Adeline "Dice" CUPP, b. 1835/6, Schuyler [now Brown] Co., IL; m. 1853, Brown Co., IL, William F. DOTY

4.  Howell Davis CUPP, b. 18 Apr 1838, Schuyler [now Brown] Co., IL; d. 24 Apr 1909, Macon Co., MO; m. 3 Feb 1860, Knox Co., MO, Mary E. SALING

5.  Absalom CUPP, b. Jun 1841/2/3, Brown Co., IL; d. 17 Jun 1915, St. Joseph, Knox Co., MO; bur. Cupp Cemetery, Knox Co., MO; m. 18 Jan 1870, Adair Co., MO, Mary WINN

6.  James CUPP, b. 2 Mar 1843/4/5, Chariton Co., MO; d. 22 Nov 1921, Adair Co., MO; m. 1 Dec 1870, Knox Co., MO, Margaret A. AUSMUS

7.  Elizabeth "Sis" CUPP, b. 1845/6, MO; m. 1 Jan 1861, Knox Co., MO, Simeon KIPPER

8.  Cynthia Ann CUPP, b. 1850, Brown Co., IL; d.s.p. 1855, Knox Co., MO

1.  Byron Sistler & Barbara Sistler.  1987.  Early East Tennessee Marriages.  Byron Sistler & Assoc., Inc., Nashville, TN (includes all extant ante-bellum marriage records from eastern Tennessee, including Claiborne Co.):  not found.

2a.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):

1830 Census	Cupp, Valentine	TN	Claiborne Co.	p. 31
1832	Cupp, Valentine	TN	Claiborne Co.

2b.  1830 Census Index and Digital Images (online at Ancestry.com; Image #58 of 101; extracted by Diana Gale Matthiesen):

1830

TN

Claiborne Co.

p. 131

Valentine Cupp

000 100 - 000 100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	15-19	1810-1815	= Valentine (b. 1811/2)
1 female	15-19	1810-1815	= Elizabeth (b. 1810)

Listed next to Valentine's father, Jacob CUPP. 

3.  1840 Census Index and Digital Images (online at Ancestry.com; Image #9-10 of 41; extracted by Diana Gale Matthiesen):

1840

MO

Chariton Co.

pp. 306A-306B

Volentine Capp

110 010 - 020 010

0200000

no slaves

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	4 or under	1835-1840	= Howell (b. 1838)
1 male	5-9	1830-1835	= Luke (b. 1832/3)
1 male	20-29	1810-1820	= Valentine (b. 1811/2)
2 females	5-9	1830-1835	= Adeline (b. 1835/6) = Martha (b. 1830)
1 female	20-29	1810-1820	= Elizabeth (b. 1810)
2	persons engaged in agriculture

Listed seven lines from Valentine's brother, Aham CUPP. 

4.  1850 Census Index/Images (online at Ancestry.com; Image #10 of 22):  Township One South Range Two West (T1S.R2W), Brown Co., IL, pp. 118B-119A, 344/346, enumerated 23/24 Aug 1850 (extracted by Diana Gale Matthiesen):

Volentine Cup	38	m	Farmer		Tenn
Elizabeth  "	39	f			"
Luke	17	m	Farmer		Ill
Dica	14	m			"
Howell	12	m			"
Absalom	7	m			"
[next page]
James Cup	15	M			Mo
Elizabeth "	4	F			"
Synthia Ann "	1/12	F			Ill

The "15" for James has to be a mistake for "5," made by the census-taker when he carried over to the next page.  Living three doors down from Edward & Rachel PERRY, in one direction; and, in the other direction, living next door to Irwin & Patsey PERRY (Sr.), who are living two doors down from Elish & Sarah PERRY, who are living next door to Irwin & Nancy PERRY (Jr.).

5a.  Census Index:  U.S. Selected Counties, 1860 (Broderbund CD-318):  not found, but there are no Missouri records on this CD.

5b.  1790-1870 Census Index (online at Ancestry.com):

1860

CUPP

VALENTINE

MO

Knox Co.

Saltriver Twp.

p. 156

6.  The Story of Liberty, Missouri. [link died]   The only battle of the Civil War fought in Clay Co., MO, was the Battle of Blue Mills Landing (a.k.a. Blue Mills Ferry).  The battle was fought in Liberty, Clay Co., across the Missouri River from Blue Mills, Jackson Co., so if Valentine died in the battle, as is said, he died in Clay Co.

7.  Jordan R. Dodd, ed.  1998.  Marriage Index: Missouri, 1851-1900.  Liahona Research, Orem, UT (Broderbund CD-234):

Cupp, Absalum

Winn, Mary

Jan 18, 1870

Adair Co.

8.  Knox County, Missouri, Marriage Records (as cited by Barbara Cupp Woods at WorldConnect):

Simeon KIPPER	Elizabeth CUPP	1 Jan 1861	Book 1845	p. 129A	#3042
James CUPP	Margaret A. AUSMUS	1 Dec 1870	Book 1845	p. 255A	#2565

9.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).

10.  LDS.  Family Search: Internet Genealogy Service:  AF - Ancestral File (online at FamilySearch.org).