1.  Marriage Record:

2.  1830 Census Index/Images (online at Ancestry.com):  not found, at least there is no John GORDON/GORDAN/GORDEN indexed in Union Co., PA.

3.  1840 Census Index/Images (online at Ancestry.com):  not found, at least there is no John GORDON/GORDAN/GORDEN indexed in Union Co., PA.

4.  1850 Census Index/Images (online at Ancestry.com; Image #10 of 33 — indexed "Nass"):  Perry [now West Perry] Twp., Union [now Snyder] Co., PA, p. 102B, 65/65, enumerated 15 Nov 1850 (extracted by Diana Gale Matthiesen):¤

Valentine Haas	79	M	None	300	Penna
Rebecka Hass	50	F			"
Gideon Gordon	15	M			"

Valentine HAAS is Rebecca's father.  Gideon GORDON is said to be the son of John GORDON & Rebecca HAAS, but the fact that Rebecca never used the surname GORDON indicates she and John were never married, so Gideon must have been illegitamate.  Either that, or Gideon is not her son.

5.  1860

6.  1870 Census Index/Images (online at Genealogy.com, Image #4 of 16):  Mt. Pleasant Mills P.O., West Perry Twp., Snyder Co., PA, Roll 1451 (Book 1), p. 205B, PN 4, 31/31, enumerated 8 Aug 1870, official enumeration date 1 Jun 1870 (extracted by Diana Gale Matthiesen):¤

Haas John	56	M	W	Farmer	4000	1000	Pa
____ Mary	48	F	W	Keeping House			Pa
____ John	14	M	W				Pa
____ Rebecca	68	F	W				Pa

The elder John HAAS is Rebecca's brother. 

7a.  LDS.  Family Search: Census Records: 1880 United States (online at FamilySearch.org):

Census Place: Perry, Snyder, Pennsylvania
Source: FHL Film #1255194; NARA Film #T9-1194; Pg 134A
	Relation	Sex	Marr	Race	Age	Birthplace	Occupation	Fa	Mo
John W. HAAS	Self	M	M	W	24	PA	School Teacher	PA	PA
Elizabeth HAAS	Wife	F	M	W	27	PA	Keeping House	PA	PA
Rebeca HAAS	Other	F	S	W	77	PA	Keeping House	PA	PA
Philip PRESLER	Other	M	S	W	22	PA	Works On Farm	PA	PA

John HAAS is Rebecca's nephew.  The link from the LDS record to the Ancestry.com image goes to the wrong page, in a different county.

7b.  1880 Census Images (online at Ancestry.com, Image #1 of 44, which is so faded, it's unreadable; online at Genealogy.com, Image #1 of 28, which is partly readable):  Perry Twp., Snyder Co., PA, Roll 1194 (Book 2), p. 134A, PN 1, SD 7, ED 153, enumerated 14 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

13

24

25

26

1

1

Haas John W

W

M

24

/

School Teacher

?

?

?

____ Elizabeth

W

F

27

Wife

/

?

?

?

____ Rebeca

W

F

77

/

Keeping house

?

?

?

Westin? Philip

W

M

22

/

Works on Farm

?

?

?

8.  George W. Wagenseller.  1904.  Tombstone Inscriptions of Snyder County, Penna.  Wagenseller Publ., Middleburgh, PA (facsimile hard copies available from HigginsonBooks.com; online at the Snyder County PAGenWeb site):

p. 177	ST. JOHN'S CEMETERY. Located at Fremont. List of deaths taken from Sexton's Record...
p. 180	Haas, Rebecca d of Valentine d June 20, 1881, aged 78 y 2 m 1 d...

9.  Birthdate calculated using Ben Buckner's JavaScript Birthday Calculator.

Name	Deathdate	Age at Death	Result
Rebecca	20 Jun 1881	1d 2m 78y	19 Apr 1803
(Calculated birthdates should always be prefaced with "ca." — you can't be certain the person who calculated their age did it correctly.)

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