INTERNET RESEARCH As of November 2003
No Johnston/Johnson are listed in the 1790 census for Allegheny County PA at index [See Regional Information for an explanation of the town and county names at various points in time]
An Alexander Johnston is recorded in Mead Township in the 1800 census of Crawford Co. which included Meadville, Mead Township and Coniott. No John Johnston/Johnson is recorded as Head of Household in that census. A John Johnston does appear in the censuses for 1810, 1820 and 1830.
Census records for John Johnston of Sadsbury Township, Crawford Co. PA from Census. [Note that Vernon Township was formed in 1829 from portions of Sadsbury and Meadville and would not have been mentioned in census records prior to 1830.
The 1820 census for Sadsbury also includes (but no others):
Arthur Johnston (aged 26-44) with a female (aged 26-44), 1 male<10 and 2 females<10
Oliver Johnston (aged 26-44) with a female (aged 26-44)
By the time of the 1830 census, Johnstons have expanded in Crawford Co. (from 1830 Crawford Co. Census Index Flaugh - McCoy)
Vernon Township: Arthur Johnston, Arthur Johnston, John Johnston, Lancelot Johnston, Oliver Johnston, Sinclair Smith (or Smith Sinclair) Johnston
Conneaut Township: William Johnston
Mead Township: Alexander Johnston, William Johnston
Meadville: Alexander Johnston, Andrew Johnston
Randolph Township: Joseph Johnston
Sadsbury Township: Ephraim Johnston, James Johnston
Sparta Township: Nathan Johnston
Woodcock Township: James Johnston, William Johnston
John Johnston, son of James and Elizabeth (Brown) Johnston, died 1830 at Mifflin PA (submitted by Earl Jay Nielsen); family all from Mifflin PA
John Johnston b. ~1758 at Knockroe, Fermanagh IRE, son of Arthur Johnston (submitted by Cheryl Bunde Youngren) with a son Arthur Johnston b. Jan. 8, 1788 at Knockroe, Fermanagh IRE, m. Margaret McClure, d. Jun. 9, 1851 [also recorded at Worldconnect]
only record for a John Johnston who died 1830 in PA OR had a father named Arthur: John Johnston b ~1794, son of James and Elizabeth (Brown) Johnston of Cumberland Co. PA, died 1830 at Mifflin Co. PA (submitted by Eric and Leigh Morris Marvin) - other children include William, Margaret, Mary, Elizabeth & Sarah. No marriage/children recorded for this John Johnston
several discussion threads on Johnston's in Mercer Co. PA but unable to make a specific connection; major thread for Arthur Johnston+Sarah Ann McKee
no reference to Mercy Johnston
In the 1885 History Vernon Township
"John Johnson, a native of Ireland, immigrated to America in 1797, and about 1800 settled within the present limits of Vernon, where he died at the age of seventy-two years in 1830, leaving a large family."
Arthur Johnston was a Ruling Elder of the Watson's Run United Presbyterian Church when the church was organized in 1869
Mentions "...Johnson's saw-mill on the same stream [Watson's Run] in the northwest part of the township."
No record at Rootsweb Worldconnect for Mercy Johnston married to Thomas Mathers (using Soundex), no record of Mercy Johnston born 1812+/-5 years in PA (or anywhere else), and no Mercy Johnston or Mercy Mathers died 1871 in PA (or anywhere else). Also, no relevant records at ancesty.com, genealogy.com or genforum.com. No web sites found in response to Google search for "Mercy Johnston"+"Thomas Mathers" or "Mercy Johnston"+"Conneaut Lake".
Searching using Google there is one hit on "Mercy Johnston" + "Thomas Mather" at Herrington - pafg08.htm - Generated by Personal Ancestral File (a Herrington web site), there is an ancestry for Edward Arthur Herrington and his wife, Eva Minerva Mather daughter of Thomas Mather and Mercy Johnston - based on material from Bill L. Petrie Feb. 26, 1992. [This was the only "hit" for "Mercy Johnston"+"Thomas Mather"]
Other Johnstons in Crawford Co., Pennsylvania:
History of the Erie Presbytery states that "The second pastor [of Meadville] was Rev. Robert Johnston (15). He was installed, October 15, 1811, as pastor of Meadville, Little Sugar Creek, and Conneaut (now Evanaburg). This relation was dissolved April 2, 1817....THIS church [at Evansburg] was formerly known as Conneaut, or the Outlet of Conneaut. In 1811 to 1817, it constituted a part of the charge of Rev. Robert Johnston, in connection with Meadville and Little Sugar Creek. It was probably dependent on supplies from that time to April 14, 1841, when Rev. Edward S. Blake (59) was ordained and installed as pastor." Original source: J. M. Eaton, History of the Presbytery of Erie, Embracing in Its Ancient Boundaries the Whole of Northwestern Pennsylvania and Northeastern Ohio: with Biographical Sketches of All Its Ministers, and Historical Sketches of Its Churches (New York: Hurd and Houghton, 1868)