1.  LDS.  Family Search: Internet Genealogy Service:  IGI - International Genealogical Index (online at FamilySearch.org).

Alexander M. GRAHAM Marriage: 19 Apr 1827, Meramec Twp, Jefferson, Missouri Spouse: Jemima JONES Source: patron submission

Samuel P. EOFF Spouse: Jemima GRAHAM Marriage: 12 Oct 1831, Jefferson, Missouri Source: Marriage Records, 1825-1951. Jefferson County (Missouri). Recorder of Deeds

Samuel Parker EOFF; Birth: 13 May 1811, Missouri; Death: 1870 Marriage: 12 Oct 1831, Jefferson, Missouri Spouse: Jemina Mamie Graham Jones; Birth: 1812, Missouri Source: patron submission

Other sources (also secondary) say Samuel's middle name was "Porter."

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

Eoff, Thomas	Davis, Clarissa	17 Jul 1856	Jefferson Co.
Eoff, Martin	Wideman, Sarah	11 Jul 1867	Jefferson Co.

3a.  1840 Census Index/Images (online at Ancestry.com):  can't find, but he should be in Jefferson Co., MO.  I did a page-by-page search of Big River Twp., but didn't find him.  The Jefferson County census is extremely difficult to read, so he may be so badly indexed that I don't recognize him.

3b.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):  can't find, and I really looked.

4.  1850 Census Every-Name-Index/Images (online at Ancestry.com; Image #50-51 of 153):  District No. 42, Jefferson Co., MO, Roll M432_402, pp. 431B-432A, 381/381, enumerated 30 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):¤•

Samuel P Eoff	39	M		Farmer		Mo
Jemima     "	38	F				Mo
William    "	14	M				Mo
Thomas     "	13	M				Mo
Mary E     "	11	F				Mo
Francis M  "	7	M				Mo
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Jasper Eoff	4	M				Mo
Newton   "	4	M				Mo
Louis M  "	2	M				Mo

5.  1860 Census Index/Images (online at Ancestry.com, Image #3 of 35):  Morse's Mills P.O., Big River Twp., Jefferson Co., MO, Roll M653_626, p. 661, PN 112, 863/853, enumerated 25 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤•

Samuel P Eoff	49	M		Farmer	300	150	Mo
Jemima Eoff	48	F					"
Jasper	13	M					"
Newton	13	M					"
Lewis M	11	M					"
Catherine	7	F					"

There's a bracket connecting Jasper and Newton with the word, "living" (I mean... what else?).  Listed next to the Madison GRAHAM household (æ 41, b. MO, wife Nancy).

6.  1870 Census Every-Name-Index/Images (online at Ancestry.com, Image #51 of 51):  Hillsboro P.O., Big River Twp., Jefferson Co., MO, Roll M593_783, p. 220A, PN 51, 372/377, enumerated 8 Jul 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤•

Eoff Newton	23	M	W	Farmer		125	Missouri
____ Margaret	20	F	W	Keeps house			do
____ Thomas	2	M	W	At home			do
____ Mary	1/12	F	W	do			do	Apl
____ Jemima	59	F	W	Lives with Son			do

7.  WorldConnect / Ancestry World Trees (online at RootsWeb.com/Ancestry.com).  From the Notes in a file there submitted by J.M. Dale:

Samuel shot and killed his son William in 1862.  On the same day, he was tried, convicted, sentenced to death, and hanged from a tree in his own yard. Another son assisted with the hanging.