1a.  Anon.  1966.  Marriage Index:  Ohio, 1789-1850.  Liahona Research, Orem, UT (Broderbund CD-400):  not found.

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

Peter DOUGHMAN Spouse: Sarah Ann MURPHY Marriage: 19 Feb 1840, Goshen, Clermont, Ohio Marriage: 19 Feb 1840, Loveland, Clermont, Ohio Sources: patron submissions

I really doubt the location.  Both Peter's parents and Sarah's parents lived in Warren Co., as did Peter & Sarah.

2.  1850 Census Index/Images (online at Ancestry.com; Image #33 of 51):  Hamilton Twp. District 149, Warren Co., OH, p. 84A/167, 1213/1214, enumerated 7 Sep 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Peter Duffman	28	M		Mason	1500	O
Sarah      "	28	F				O
Margaret J "	10	F				O
Fraetta?   "	8	F				O
Sarah E    "	6	F				O
Eleanor J  "	4	F				O

Living next door to Benjamin DUFFMAN (æ 27, b. O, mason, wife Anna).

3.  1860 Census Images (online at Ancestry.com; Image #7 of 98):  Morrow P.O., Salem Twp., Warren Co., OH, p. 121A, PN 1, 51/52, enumerated 18 Jul 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

Peter Doughman	41	M		Mason	2300	395	O
Sally A   "	38	F		Housewife			Delaware
Margaret  "	19	F		House Keeper			O
Floretta  "	16	F					O
Sarah E   "	13	F					O
Mary E    "	11	F					O

4.  1870 Census Images (online at Ancestry.com; Image #30 of 56):  Maineville P.O., Hamilton Twp., Warren Co., OH, p. 310A, PN 29, 226/223, enumerated 14 Jun 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Doughman Peter	51	M	W	Journeyman Stone Mason	4000	500	Ohio
________ Sarah	48	F	W	Keeping House			Delaware
________ Mary E	20	F	W	Helps Mother			Ohio

5.  1880 United States Census and National Index (LDS Family History Resource File: CD-ROM Library):

Census Place: Hamilton, Warren, Ohio
Source: FHL Film 1255075; NARA Film T9-1075; Pg 294C
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
Peter DOUGHMAN	Self	M	M	W	62	OH	Stone Mason	PA	PA
Sarah A. DOUGHMAN	Wife	F	M	W	58	DE	Keeping House	DE	DE
Rachel DOUGHMAN	Dau	F	S	W	30	OH	Servant	OH	DE
Eva DOUGHMAN	Dau	F	S	W	25	OH	Servant	OH	DE
Adie DOUGHMAN	Dau	F	S	W	19	OH		OH	DE
Ada DOUGHMAN	Dau	F	S	W	19	OH	Servant	OH	DE
Estella DOUGHMAN	Dau	F	S	W	16	OH	Servant	OH	DE
Charles DOUGHMAN	Son	M	S	W	12	OH	At School	--	--
Eve WADKINS	Mother	F	W	W	82	PA		PA	PA
Louey DOUGHMAN	GDau	F	S	W	5	OH		OH	OH