Nancy's birth and death dates appear to be from a tombstone, and it appears she had been fibbing about her age, as widows are inclined to do.  The "before 1794" date indicated in the census is much more plausible.

— born in KY or IL:
  5.  Louisa Jane CHRISMAN, b. 18/11 Sep 1822
  6.  William Riley CHRISMAN, b. 18 Jul 1824
  7.  John Bobbitt CHRISMAN, b. 3 Feb 1826

— born in IL:
  8.  Emsley J. CHRISMAN, b. 25 Feb 1829 
  9.  James Marion CHRISMAN, b. 8 Oct 1831
10.  Michael N. CHRISMAN, b. 18 Jun 1834
11.  Lorenzo Van CHRISMAN, b. 6 Apr 1837; m. 26 Jun 1856, Scott Co., IL, Mary Jane V. FILMER

1a.  Jordan R. Dodd, ed.  1993.  Kentucky Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-229):

Chrisman, John

Bobbitt, Nancy

22 Dec 1811

Christian Co.

1b.  Anon.  1983/96.  Kentucky Marriage Records: from the Register of the Kentucky Historical Society.  Genealogical Publ. Co., Baltimore, MD (Broderbund CD-519).  On p. 100:

Chrisman, John

Bobbit, Nancy

22 Dec., 1811

Ishum Bobbit

2.  1820 Census Index and Digital Images (online at Ancestry.com; Image #7 of 23 — mis-indexed "Chriman"; extracted by Diana Gale Matthiesen):

1820

KY

Christian Co.

p. 34

Ln. 12

John Chrisman

200010-20011-0-100

0000-0010

These data indicate:ves

No., Race, Gender	Age Class	Therefore Born	Individuals Inferred
2 white males	9 or under	1810-1820	= Willis (b. 1818) = Presley (b. 1816)
1 white male	26-44	1775-1794	= John (b. 1791)
2 white females	9 or under	1810-1820	= Emily (b. 1820) = Annice (b. 1814)
1 white female	26-44	1775-1794	= Nancy
1 white female	45 or over	in or bef. 1775	= grandma?
1	people engaged in agriculture
1 female slave	26-44	1775-1794	= ?

Listed 13 lines from John's father, George CHRISMAN, Sr., who is two lines from John's sister, Barbara (CHRISMAN) BOBBITT, who next to John's brother, George CHRISMAN, Jr. 

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

1830 State Census

Christman, John

IL

Morgan Co.

p. 17

4.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):  John not found in Morgan Co., IL.

5.  Census Index:  U.S. Selected Counties, 1850 (Broderbund CD-317):  Nancy not found.

6a.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1810-1813.   (Self-published; available from author at 4396 Coopertown Rd., Russellville, KY 42276, or from the Christian County Genealogical Society, Hopkinsville, KY).

Pg. in Willhite	Year	First  Name	Last  Name	A	B	C	D	E	Acres	Watercourse
-	1810-12	-	-	-		-	-	-	-	-
161	1813	John	Chrisman	1		-	-	3	-	-
Legend for numerical data: A = White Males 21 or over; B = White Males 16-20 (this column used only in 1811); C = Blacks over 16; D = Total Blacks; E = Horses

6b.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1814-1818.   (Self-published.  This book is out of print.  I do not have a copy.  If you have one to sell, please contact me.)

6c.  A.B. Willhite.   [n.d.]  Christian Co., Kentucky, Tax List, 1819-1823.   (Self-published; available from author at 4396 Coopertown Rd., Russellville, KY 42276, or from the Christian County Genealogical Society, Hopkinsville, KY).

Pg. in Willhite	Year	First Name	Last  Name	A	B	C	D	Acres	Watercourse
15	1819	John	Christman	1	-	-	3	150	T W
83	1820	John	Christman	1	-	-	4	150	T W
126	1821	John	Christman	1	-	-	2	150 100	Sand Lick "
169	1822	John	Christman	1	-	-	3	150	T W
213	1823	John	Christman	1	-	-	2	150 107	T W T W
Legend for numerical data: A = White Males 21 or over; B = Blacks over 16; C = Total Blacks; D = Horses
Abbreviations:  TW = Tradewater River

7.  Anon.  1993.  Christian County, Kentucky, Wills and Estates, 1815-1823:  Christian County Will Book C.  T.L.C. Genealogy, Miami Beach, FL.
"C Court" = Christian County Court.

p. 78

Page 315. Inventory. We, agreeable to an order of C Court at their May Term 1820, have proceeded, after first being sworn, to appraise the personal estate of John Keys deceased (or such therof as was produced to us). Total amt: $43.14½.  Signed May 27, 1820 - John Chrisman, Jas. C. clark, Tho. Dunkerson...

8a.  John CHRISMAN not found in Court Order Book A nor in Book B, Part 1.

8b.  James Taylor Killebrew.  1987.  County Court Order Book "B" Part 2 for Christian County, Kentucky, for the years Nov. 1809 - 6 June 1814 for a County Court held at Town of Hopkinsville.  Christian County Family and History Research Society (4465 Cadiz Rd., Hopkinsville, KY 42240).  First column is the page number in Killebrew; second column is the page number in Court Order Book B.

p.	p.	Date	Motions
131	346	6 Sep 1813	Ordered that James Palmer be appointed surveyor of that part of the road from Hopkinsville to the United States Saline commenceing (sic) at the Sinking Fork and continuing to a marked Black Oak about half a mile from Bobbitts and be assisted by the following hands to wit: ... George Christman, John Christman ...

8c.  There are no Court Order Books "D" or "E"; the letters were skipped.

8d.  James Taylor Killebrew.  1999.  County Court Order Book "F," Parts 1 & 2 [but not Part 3], Christian County, Kentucky, for the years 1819-1825.  County Genealogical Society (1101 Bethel St., Hopkinsville, KY 42240).  First column is the page number in Killebrew; second column is the page number in Court Order Book F.

p.	p.	Date	Motions
83	81	1 May 1820	On motion of the administrator of John Keyes deceased it is ordered that John Chrisman, James Clark and Thomas Dunkerson after being first duly sworn before a magistrate do appraise in current mony the personal estate and slaves if any of said decedent and report thereof.
358	344	6 Dec 1824	On motion of Francis Boyd, the Viewers appointed by a former order of the Court to view and mark the nearest and best way for a road leading from Hopkinsville to Williamson's Mill on Trade Water having heretofore made their report and the Court being fully advised of and concerning the premises, it is ordered that said road be established agreeable to said report. ----- And it is further ordered that Michael Workman be appointed Surveyor of said road from the Saline Road to the Cove Lick and that Abner Boyd be appointed Surveyor of said road from the Cove Lick to Francis Boyds and that John Chrisman be appointed Surveyor of said road from Francis Boyds to James Clarks and Lemuel Clark from James Clarks to Williamsons Mill and that the said Surveyors open the said road and keep it in lawful repair and that all the hands residing within three miles on each side thereof be alloted to work on said road.
380	363	8 Mar 1825	Ordered that John Chrisman be appointed Surveyor of that part of the road leading from Hopkinsville to Williamson's Mill Commencing at Francis Boyds and continuing to John Keys and that the following hands be alloted to work on said part of said road, to wit:  David Clark 1 hand, John Chrisman 1 hand, Peter Chrisman (1), George Chrisman (1), Luton Lewis (1), William Underwood (1), Samuel Underwood (1), James Knight (1), John Knight (1), Jacob Chrisman (1), George Chrisman, Jr. (1), William Long (1), Thomas Long (1), James Johnston, Robt. Philps (1), Joshua Bryant (1), Lawrence Bryant (1) Andrew Maun [sic, Mann] (1), William Brawnon (1), John Keys (2) hands.

9.  Descendants of William Bobbitt by Linda D. Martin. [link died]

10.  Email from Marcelle Porter (25 Jun 2000).

11.  WorldConnect (online at RootsWeb.com).

12.  Jordan R. Dodd, ed.  1993.  Illinois Marriages:  Early to 1850.  Liahona Research, Orem, UT (Broderbund CD-228):

Chrisman, Prisley	Bryant, Frances M.	Dec 17, 1840	Sangamon Co.
Chrisman, Willis	Bryan, Rachael Jane	Dec 22, 1842	Sangamon Co.

13.  Jordan R. Dodd, ed.  1998.  Marriage Index:  Illinois, 1851-1900.  Liahona Research, Orem, UT (Broderbund CD-250):

Chrisman, John B.	Graves, Zilpha Ann	Apr 12, 1857	Morgan Co.
Chrisman, Prisley A.	McComas, Nancy	Mar 10, 1859	Sangamon Co.

"John B." may not be John Bobbit CHRISMAN.

14.  Illinois Statewide Marriage Index, 1763–1900:

CHRISMAN, LORENZO V

FILMER, MARY JANE V

SCOTT

06/26/1856

____/0087

00001537