1.  Marriage Record:

2.  1880 Census Every-Name-Index/Images (online at Ancestry.com):  can't find, and I really looked.  Margaret is married, so, as expected, she is not with her parents.

3.  1890 Census:  the 1890 Census Population Schedules were destroyed.

4.  1900 Census Every-Name-Index/Images (online at Ancestry.com, Image #14 of 18):  Millcreek Twp., Clarion Co., PA, Roll T623_1395 (Book 1), p. 207B, SN 7, SD 14, ED 16, enumerated 15 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	26	27	28
111	112	Morrow Maggie	Head	W	F	Oct 1853	46	M	27	4	2	PA	PA	PA	Farmer	0	Y	Y	Y	O	M	F	100
		______ Lottie ?	Dau	W	F	Feb 1884	16	S				PA	PA	PA			Y	Y	Y

Listed next to Philip F. STROUP, first cousin of James Sterrett STROUP.

5.  1910 Census Every-Name-Index/Images (online at Ancestry.com, Image #15 of 15):  Mill Creek Twp., Clarion Co., PA, Roll T624_1329, p. 284A, SN 8A, SD 18, ED 16, enumerated 25 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	23	24	25	26	27	28	29
125	127	Morrow Margrete A	Head	F	W	56	M	22	4	3	PA	PA	PA	Eng	Farmer	General farm	Emp	Y	Y		O	F	F	104
		Stroup Arthur L	GSon	M	W	11	S				PA	PA	PA	Eng	None			Y	Y	Y

Listed three households from Arthur's paternal grandparents, James Sterrett & Mary (GRADY) STROUP.

6.  1920 Census Every-Name-Index/Images (online at Ancestry.com, Image #3 of 10):  Fisher, Millcreek Twp., Clarion Co., PA, Roll T625_1551, p. 250A, SN 2A, SD 18, ED 73, enumerated 9/10 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).
2	3	4	5	6	7	8	9	10	11	12	17	18	19	21	23	25	26	27	28	29
Fm	30	30	Morrow Marguerite	Head	O	F	F	W	63	W	Y	Y	PA	PA	PA	Y	None	General farm	Oa	29
			______ Arther	GSon			M	W	21	S	Y	Y	PA	PA	PA	Y	Farmer	General Farm	Em

7.  Deaths Recorded 1925-1932.  Clarion County Historical Society Library (online at the Clarion County PAGenWeb site):

Name	Birth	Death	Age	Father	Mother
Morrow, Margaret Ann	10-5-1853	8-4-1926	72-9-9	Henry Hillard	Carolene Guentrum

8.  Fisher Methodist Cemetery, Mill Creek Township (online at the Clarion County PAGenWeb site; transcribed by Nate Zipfel):

Last Name	First Name	Middle Name	Date of Birth	Date of Death
Morrow	Margaret	A	1853	1926
Morrow	Maude	M	1880	1899

These are the only MORROWs listed in the cemetery.  It's extremely likely that Maude is one of Margaret's two children who died before 1900.