1.  Marriage Record:

2.  1850 Census Index/Images (online at Ancestry.com; Image #66 of 299):  Spring Gardens (Ward 3, Precinct 1), Philadelphia Co., PA, p. 478B, 436/___, enumerated 2 Aug 1850, official enumeration date 1 Jun 1850 (extracted by Diana Gale Matthiesen):

Mira Cobb	36	F				Pennsylvania
Margaret Cobb	18	F				"
Edward Cobb	16	M		Printer		"
Henry Cobb	9	M				"
Daniel Cobb	6	M				"
William K/R Parks	20	M		Umba Maker		"

3.  1860 Census Images (online at Ancestry.com; Image #203-204 of 780):  Philadelphia (Ward 1, Precinct 4), Philadelphia Co., PA, pp. 203-204, PN 29-30, enumerated 7 Jun 1860, official enumeration date 1 Jun 1860 (extracted by Diana Gale Matthiesen):

236	247	William R. Park	31	M		Umberella Maker		50	Penna
		Margaret     "	28	F					"
[next page]
		Myra C Park	9	F					Penna
	248	Myra Cobb	47	F		Glove Maker		300	"
		Henry Q "	20	M		Plumber			"
		Daniel B "	16	M		Clerk			"

Myra COBB is Margaret's mother; Henry and Daniel are Margaret's brothers.

4.  1870 Census Index/Images (online at Genealogy.com; Image #4 of 246):  Philadelphia P.O., Philadelphia (Ward 1, District 2), Philadelphia Co., PA, Roll 1387, p. 453B, PN 14, 30/30, enumerated 2 Jun 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):

Park Wm R	39	M	W	Engineer	5000	300	Penna
____ Margaret	38	F	W	Keeping house			Penna
____ Mira	19	F	W	at home			Penna
Cobb Mira	36	F	W	at home			Penna

Is Mira COBB's age correct?  If so, she would be Margaret's unmarried sister, not her mother.  I'm more inclined to think the enumerator erred (Myra should be 56, not 36), especially as no younger Myra is present in 1860.

5.  1880 Census Every-Name-Index/Images (online at Ancestry.com, Image #12 of 22):  1319 South Fifth Street, Philadelphia, Philadelphia Co., PA, Roll T9_1167, p. 414D, PN 12, SD 1, ED 26, enumerated 4 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

9

10

11

13

24

25

26

*

1319

107

111

Parks W K?

W

M

51

/

Chief Enginner Gas Works

PA

PA

PA

_____ M F

W

F

47

Wife

/

House Keeping

PA

PA

PA

_____ M C

W

F

27

Dau

/

At Home

PA

PA

PA

Cobb M C

W

F

67

M-in-law

/

PA

PA

PA

____ Eva

W

F

17

Niece

/

At Home

PA

PA

PA

*South Fifth Street

6.  1890 Census:  the 1890 census population schedules were destroyed.

7.  1900 Census Index/Images (online at Genealogy.com; Image #319 of 600):  1214 S Broad [St?], Philadelphia (Ward 26), Philadelphia Co., PA, Roll 1468, p. 163B, SH 10, SD 1st Pa, ED 627, enumerated 5 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	19	20	22	23	24	25	26	27
189	239	Park Wm K	Head	W	M	Oct 1827	72	M	50			PA	PA	PA			Engenier	0	Y	Y	Y	O	F	H
		____ Margaret F	Wife	W	F	Nov 1831	68	M	50	2	1	PA	PA	PA					Y	Y	Y
		Cobb Myra	M-in-Law	W	F	Aug 1812	77	Wd		6	4	PA	PA	PA					Y	Y	Y
		McCarty Bridget	Servant	W	F	Feb 1863	37	S				Ire	Ire	Ire	1880	20	Servant	0	Y	Y	Y

Myra is 87, not 77.