Elizabeth is said to have died in Aug 1954, which would make her 100 years old at death.  I can't find her in the 1930 census, so I wonder if someone hasn't made a typo and her deathyear shouldn't be 1924.

1.  Marriage Record:

2.  1890 Census:  the 1890 Census Population Schedules were destroyed.

3.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #14 of 28):  117 College Avenue, Des Moines City (Ward 4), Des Moines Twp., Polk Co., IA, Roll T623_454 (Book 1), p. 184B, SN 7, SD 80, ED 88, enumerated 7 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

16

17

18

19

20

21

22

23

24

25

26

27

*

117

16

151

Jackson Joshua E

Head

W

M

Jul 1847

52

M

16

Ire

Ire

Ire

1863

37

Na

Capitalist

0

Y

Y

Y

O

F

H

_______ ????

Wife

W

F

??? 1852

47

M

16

6

6

IA

PA

PA

Y

Y

Y

_______ ????

Dau

W

F

Dec 1884

15

S

IA

Ire

IA

At School

9

Y

Y

Y

_______ John

Son

W

M

Jul 1886

13

S

IA

Ire

IA

At School

9

Y

Y

Y

_______ Richard

Son

W

M

May 1888

12

S

IA

Ire

IA

At School

9

Y

Y

Y

_______ Charlotte

Dau

W

F

Jan 1890

10

S

IA

Ire

IA

At School

9

Y

Y

Y

_______ Alma

Dau

W

F

Feb 1892

8

S

IA

Ire

IA

At School

9

_______ Joshua

Son

W

M

Sep 1896

3

S

IA

Ire

IA

*College Avenue

There are two ink blobs on the record, so I can't read the given name of the wife or eldest daughter's name, but it's a short name, so it must be Mary.

4.  1910 Census Every-Name-Index/Images (online at Ancestry.com, Image #18 of 27):  117 College Ave., Des Moines City (Ward 4), Polk Co., IA, Roll T624_420 (Book 1), p. 9B, SH 9B, SD 7, ED 120, 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

15

16

17

18

23

24

25

26

27

28

*

117

210

221

Jackson Joshua E

Head

M

W

63

M1

26

Ireland Eng

Ireland Eng

Ireland Eng

?

?

Eng

None

Y

Y

O

F

H

_______ Elizabeth S

Wife

F

W

55

M1

26

6

6

Iowa

Pennsylvania

Pennsylvania

Eng

None

Y

Y

_______ Mary S

Dau

F

W

25

S

Iowa

Ireland Eng

Iowa

Eng

None

Y

Y

Y

_______ Elizabeth D

Dau?

F

W

24

S

_______ John S

son

M

W

23

S

Iowa

Ireland Eng

Iowa

Eng

None

Y

Y

Y

_______ Alma S

Dau

F

W

18

S

Iowa

Ireland Eng

Iowa

Eng

None

Y

Y

Y

Stroup Mary

M-in-law

F

W

87

Wd

13

6

Pennsylvania

Pennsylvania

Pennsylvania

Eng

None

Y

Y

* College Ave

The enumerator tried to squeeze a daughter in-between Mary and John, then lined it out with this note in the margin:  "Transferred to sheet 100 line 49."  I couldn't find sheet 100, but the daughter is in the index, so I've included her (Elizabeth D. JACKSON).  On the other had, Elizabeth is not with them in the 1900 census, and the mother says she's only had six children, so is she really their daughter?  The two STOKES children indexed with them belong to the STOKES household above them.

5.  1920 Census Every-Name-Index/Images (online at Ancestry.com, Image #7 of 45):  1023 Eighteenth Street, Des Moines City (Ward 1), Precinct 5, Polk Co., IA, Roll T625_507 (Book 2), p. 125A, SN 4A, SD 7, ED 82, enumerated 5 Jan 1920, official enumeration date 1 Jan 1920 (extracted by Diana Gale Matthiesen):¤•

1920:  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
*	1023	84	87	Jackson Joshaway	Head	O	M	M	W	72	M	1859	NA	Y	Y	Ire	Eng	Ire	Eng	Ire	Eng	Y	Farmer	Retired	OA
				_______ Elisebeth	Wife			F	W	65	M			Y	Y	IA		PA		PA		Y	None
*Eightheenth (sic) Street

6.  1930 Census Every-Name-Index/Images (online at Ancestry.com):  Joshua is deceased, but I can't find Elizabeth, either.

7.  Iowa Family Group Sheet for the Joshua Edward JACKSON Family (online at the IAGenWeb site; contributed by Shirley Jackson).

8.  LDS.  Family Search: Internet Genealogy Service:  AF - Ancestral File (online at FamilySearch.org).

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