I'm following secondary sources in giving our subject this wife, but, in fact, I've found no proof the William WALKER who married her is the same William WALKER who married Harriet Ann DANT and Mary Ellen LAVELY.

1.  Works Progress Administration.  Indiana Marriage Collection, 1800-1941 (online at Ancestry.com):

William D Walker	Harriol A Dant	22 Jun 1853	Daviess Co.	Book 1, p. 635
William Walker	Mary Evaline Rogerson	30 Aug 1855	Daviess Co.	Book 3, p. 347
William D Walker	Harriet A Dant	22 Jun 1858	Daviess Co.	Book 1, p. 635
William B Walker	Mary Ellon Lavely	11 Jan 1870	Daviess Co.	Book 3, p. 136

These WPA extractions are rife with errors.

2a.  1860 Census Every-Name-Index/Images (online at Ancestry.com, Image #59 of 62):  Black Oak Ridge P.O., Barr Twp., Daviess Co., IN, Roll 251, p. 797, PN 60, 482/478, enumerated 25 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):¤-

William Walker	27	M		farmer & carpenter	100	300	Indiana
Harietan  "	21	F					Indiana
Maryan    "	2	F					Ind

Harietan = Harriet Ann; she's indexed "Narietan."

2b.  1860 Census Every-Name-Index/Images (online at Ancestry.com):  Mary Ellen LAVLY (æ 22, b. IN) is living in Barr Twp., Daviess Co., IN (p. 789), with her parents, William LAVLY (æ 57, b. KY) & Mary (æ 52, b. KY), plus siblings.

3.  1870 Census Every-Name-Index/Images (online at Ancestry.com, Image #61 of 66):  Washington P.O., Barr Twp., Daviess Co., IN, Roll M593_306, p. 168A, PN 61, enumerated 24 Jun 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤-

1870:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
1	2	3	4	5	6	7	8	9	10	14	15	19
427	413	Walker William B	36	M	W	Farmer	3200	1000	Indiana	Jany		/
		______ Mary E	32	F	W	Keeping house			Indiana	Jany
		______ Mary A	11	F	W				Indiana		/
		______ Lydia I	9	F	W				Indiana		/
		______ Henry E	7	M	W				Indiana		/
428		______ Benjamine	5	M	W				Indiana
		______ Ignatius A	3	M	W				Indiana

4a.  1880 Census Every-Name-Index/Images (online at Ancestry.com, Image #1 of 3):  Cannelburg, Daviess Co., IN, Roll T9_271, p. 464D, PN 24, SD 1, ED 137, enumerated 23 Jun 1880, official enumeration date 1 Jun 1880 (extracted by Diana Gale Matthiesen):¤-

1880:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
1	2	3	4	5	6	8	11	13	15	21	24	25	26
195	198	Walker Mary E	W	F	40		\	Keeping hous	Billeous Fever		IN	KY	KY
		Amand L	W	F	9	Dau				\	IN	IN	IN

4b.  1880 Census Every-Name-Index/Images (online at Ancestry.com):

• Mary WALKER (æ 21, b. IN/IN/IN) is living in Washington Twp., Daviess Co., IN (p. 579A), as a domestic servant with the MURPHY family.
• Lydia WALKER (æ 19, b. IN/KY/IN) is living in Washington Twp., Daviess Co., IN (p. 547B), as a domestic servant living with KELLENBERGER family.
• Henry E. WALKER (æ 17, b. IN/IN/IN) is living in Barr Twp., Daviess Co., IN (p. 462D), as a farm laborer with the DONOHUE family.
• Benjamin F. WALKER (æ 17, b. IN/IN/IN) is living in Veale Twp., Daviess Co., IN (p. 502B), with his aunt & uncle, Willis E. WALLACE (æ 35, b. IN) & Nancy J. (RUNNELS) WALLACE (æ 31, b. IN), and their children.  Is he really their nephew?
• Ambros WALKER (æ 3, b. IN/IN/IN) is living in Barr Twp., Daviess Co., IN (p. 463B), with his widowed aunt, Jane (DANT) CAMPBELL (æ 21, b. IN), and her son.

6.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #2 of 37):  Barr Twp. (East half), Daviess Co., IN, Roll T623_365 (Book 1), p. 142B, SN 1, SD 2, ED 1, enumberated 4 Jun 1900, official enumeration date 1 Jun 1900 (extracted by Diana Gale Matthiesen):¤-

1900:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

19

20

22

23

24

25

27

28

14

14

Carrico Lewis

Head

W

M

May 1869

31

M

2

IN

KY

IN

Farmer

0

Y

Y

Y

R

F

11

_______ Lorretta

Wife

W

F

Mar 1871

29

M

2

2

2

IN

IN

IN

Y

Y

Y

_______ Ellen L

Dau

W

F

Aug 1898

2

S

IN

IN

IN

_______ William R

Son

W

M

Jan 1900

4/12

S

IN

IN

IN

Walker Mary E

M-in-Law

W

F

Sep 1838

61

Wd

2

2

IN

KY

KY

Y

N

Y

Grider William A

Boarder

W

M

Mar 1880

20

S

IN

IN

IN

Teamster

6

Y

Y

Y

7.  1910 Census Every-Name-Index/Images (online at Ancestry.com, Image #5 of 29):  Barr Twp., Daviess Co., IN, Roll T624_344, p. 7A, SN 7A, SD 2, ED 1, enumerated 23 Apr 1910, official enumeration date 15 Apr 1910 (extracted by Diana Gale Matthiesen):

1910:  for an explanation of the column headings, please see What the Numbers in the Federal Census Mean (missing columns contained no data).
1	2	3	4	5	6	7	8	9	10	11	12	13	14	17	18	19	20	21	22	23	24	25	26	27	28	29
106	107	Carrico Louis	Head	M	W	39	M1	12			IN	KY	KY	Eng	Labor	Coal Mine	W	N	0	Y	Y		O	M	F	40
		_______ Mand L	Wife	F	W	37	M1	12	6	6	IN	IN	IN	Eng	None					Y	Y
		[Louis & Mand's six children]
		Walker Mary E	M-in-Law	F	W	71	WD				IN	KY	KY	Eng	own Income										Y
		Dant Beldus	Nephew	M	W	22	S				IN	IN	IN	Eng	Labor	Coal Mine	W	N	0	Y	Y

Mand is indexed "Maud."

8.  1920 Census Every-Name-Index/Images (online at Ancestry.com):  Mary not found.

9.  Public Member Trees (online at Ancestry.com).

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