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

Bell, Caleb N.	Greenfield, Mary	Oct 16, 1837	Todd Co.
Mills, John N.	Bell, Eliza Jane	May  7, 1845	Todd Co.

2.  1820

3.  1830

4a.  1840 Census Index (online at GenealogyLibrary.com):

1840

Bell, Caleb N.

KY

Todd Co.

Todd City

p. 245

There's no such place as "Todd City," it's a mis-interpretation of "Todd Cty."

4b.  1840 Census Index/Images (online at Ancestry.com, Image #6-7 of 65 — list was roughly alphabetized; extracted by Diana Gale Matthiesen):

1840

KY

Todd Co.

Todd

Roll 124

pp. 244B-245A

Ln. 16

Bell Caleb N

100 010 001 - 001 100 100

661100-321120

0/12/00000

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 white male	4 or under	1835-1840	= Caleb (b. 1838)
1 white male	20-29	1810-1820	= John (b. 1817)
1 white male	60-69	1770-1780	= Caleb (b. 1788)
1 white female	10-14	1825-1830	= Eliza (b. ca. 1826)
1 white female	15-19	1820-1825	= Mary (b. ca. 1821)
1 white female	40-49	1790-1800	= Mary
6 male slaves	9 or under	1830-1840	= ? ? ? ? ? ?
6 male slaves	10-23	1816-1830	= ? ? ? ? ? ?
1 male slave	24-35	1804-1816	= ?
1 male slave	36-54	1785-1804	= ?
3 female slaves	9 or under	1830-1840	= ? ? ?
2 female slaves	10-23	1816-1830	= ? ?
1 female slave	24-35	1804-1816	= ?
1 female slave	36-54	1785-1804	= ?
2 female slaves	55-99	1740-1784	= ? ?
12	persons employed in agriculture

There's no such place as "Todd" in Todd County; it's a mis-interpretation of "Todd Cty."

5.  1850 Census Index/Microfilm (online at GenealogyLibrary.com — mis-indexed as "C.W. Bell," but the middle initial is definitely an "N"):  District No. 1, Todd Co., KY, p. 238, 627/632, enumerated 5 Sep 1850 (extracted by Diana Gale Matthiesen):

C N Bell	62	M	Farmer	8000	NC
Mary	50	F			"
Caleb	12	M			Ky
Montgomery	10	M			"

Listed next to Caleb's son, John BELL (& Sarah BROWDER).

6.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #68 of 169 — indexed "C.W. Bell," but the middle initial is definitely an "N"):  Elkton P.O., Todd Co., KY, Roll M653_396, p. 738, PN 68, 476/476, enumerated 13 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

C N Bell	78	M		F	18,800	25,000	NC
M Bell	60	F					NC
W M Bell	20	M		F			Ky
M E Millson?	20	F					Ky
Allice J	11	F					M O?
C M Bell	22	M		F		1,800	Ky

7.  1870 Census Every-Name-Index/Images (online at Ancestry.com; Image #127 of 328):  Fairview P.O., Fairview Precinct, Todd Co., KY, p. 374A, PN 9, 66/66, enumerated 31 Aug 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Bell Caleb N	82	M	W	farmer	18200	19000	North Carolina
____ William M	30	M	W	farmer		3000	Kentucky

8.  Todd County, Kentucky.  Deed Book M, 1839-1840 (LDS Film No. 355909; abstracted by Diana Gale Matthiesen):

p. 110

9 Nov 1839 Grantors, of Todd Co., KY =  Gideon THOMPSON and wife, Nancy; Caleb N. BELL and wife, Mary. Grantees = John BUNCH and wife, Lucy. $182 for 26 acres on the Elk Fork of the Red River.

Gideon THOMPSON is Mary (THOMPSON) BELL's father.

9a.  J.H. Battle, ed.  1884.  History of Todd County, Kentucky.  F.A. Battey Publ. Co., Chicago.

WILLIAM M. BELL, "Roseheath."  The subject of this sketch is a native of Todd County, Ky., and was born in his present residence, June 25, 1840.  His father, Rev. Caleb N. Bell, was born in 1788, in Beaufort, N.C., was an itinerant Methodist preacher in Virginia, removed to Kentucky in 1820, and died here in 1872 having been a useful minister of the Gospel for sixty-two years.  He was thrice married, and his children are:  Martha A. (Greenfield), John W., Mary S. (Clark), Eliza J. (Mills), Caleb M. and subject, who received a classical education at Emery and Henry College, of Virginia.  Subject is a farmer by profession, having 300 acres of first-class land near "Bell's Chapel."  His brick residence was built in 1828 by his father, by whom the place was originally cleared and improved.  In 1862 Mr. Bell was accidentally crippled in such a manner as to disable him for life, and he consequently employs much of his time in literary pursuits, being one of the most extensively read and well posted men in the county.  Being unmarried, his fine farm and books claim his chief attention.  He is a member of the Grange; in religion is a Methodist, and in politics is identified with the Democratic party.

9b.  Biographical sketch of John F. BELL, Caleb's grandson, on pp. 288-289, under the heading "Elkton Precinct": 

...Rev. Caleb N. Bell, who was born in 1788, in Beaufort, N.C.  Caleb Bell was for several years a traveling minister in the Methodist Church of Virginia, and for many years a local preacher in this State.  He died in 1872; he was three times married; first, to Judith H. Moore; second, to Jane Browder, and last to Mary Greenfield.  John W. Bell was born in Virginia in 1817, came to Kentucky with his parents in 1821, and to Todd County the following year...

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