One secondary source has Mary born Thaleischweiler, Bayern, Pfalz [now Thaleischweiler-Fröschen, Rhineland-Pfalz, Germany], which may be her parent's birthplace, if not her own.

— born in Fairfield Co., OH:
11.  David MOREHART, b. 4 Mar 1806

1.  Anon.  1966.  Marriage Index:  Ohio, 1789-1850.  Liahona Research, Orem, UT (Broderbund CD-400):

Morehart, Christian	Roller, Lydia	Mar  7, 1816	Fairfield Co.
Morehart, Adam	Dunkel, Elizabeth	Mar 14, 1836	Fairfield Co.

2.  1790 Census Index and Digital Images (online at Ancestry.com; Image #1 of 3; extracted by Diana Gale Matthiesen):

1790

PA

Northampton Co.

Penn Twp.

p. 20/178

John Morehart

1-1-2-0-0

These data indicate:

Gender and Type	Age Class	Therefore Born	Individuals Inferred
1 free white males	16 or over	in or bef. 1774	= John (b. 1758)
1 free white males	15 or under	1774-1790	= Jacob (b. 1783) = John (b. 1785) = Christian (b. 1787)
2 free white females	all ages	in or bef. 1790	= Mary (b. 1756) = Elizabeth (b. 1786)

Is the enumerator wrong or did they later adopt the older boys?  This John is the only MOREHART (or variation) on the CD. 

3a.  Census Index:  U.S. Selected Counties, 1800 (Broderbund CD-312).    Please see my WARNINGS regarding use of this database (the numerical data have the genders switched). 

1800

Mohrhart, John

PA

Northampton Co.

p. 613

21010-1201000

3b.  1800 Census Index and Digital Images (online at Ancestry.com; Image #48 of 66; extracted by Diana Gale Matthiesen):

1800

PA

Northampton Co.

Penn Twp.

p. 613

John Mohrhart

12010-21010-00

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
1 male	9 or under	1790-1800	= Adam (b. 1799)
2 males	10-15	1784-1790	= Christian (b. 1787) = John (b. 1785)
1 male	26-44	1755-1774	= John (b. 1758)
2 females	9 or under	1790-1800	= Christina (b. 1797/8) = Eve (b. 1796)
1 female	10-15	1784-1790	= Elizabeth (b. 1786)
1 female	26-44	1755-1774	= Mary (b. 1756)

We know that John and Christian survived to marry, so is Jacob the one who died by 1800?  Or has Jacob just left home (he is 17)?  John is the only MOREHART (or variation) on the CD.

5.  Census Index:  U.S. Selected Counties, 1810 (Broderbund CD-313):  not found, but the 1810 census of Ohio was lost (except for Washington Co.).  There are no MOREHARTs (or variations) on the CD.

6.  Census Index:  U.S. Selected Counties, 1820 (Broderbund CD-314):

1820

Morehart, Mary

OH

Fairfield Co.

Rush Twp.

p. 110

7.  Census Index:  U.S. Selected Counties, 1830 (Broderbund CD-315):

1830

Morehart, Mary

OH

Fairfield Co.

Bloom Twp.

p. 163

8.  Census Index:  U.S. Selected Counties, 1840 (Broderbund CD-316):  not found.

9.  John T. Humphrey.  1991-1998.  Pennsylvania Births.  14 vols.  Self-published, Washington, DC (Broderbund CD-196):

Child: J. Michel Morheadt Birth/Baptism Date: 12 Mar 1758 Date Comment: Baptism Location: New Goshenhoppen Reformed, Upper Hanover Township County: Montgomery State: Pennsylvania Father: Jacob Morheadt Mother: Mrs. Anna Morheadt

This record is presumed to be that of Johannes/John MOREHART, but typically, an individual baptized Johan Michel would have gone by Michael.  When "John" is the saint's name (the first given name in German naming practice), it is usually spelled Johan or Johann (or Hans), not Johannes.

10.  WorldConnect (online at RootsWeb.com).

11.  Broderbund.  World Family Trees.  Vol. 2, Pedigree #601.  Gives these notes for John MOREHART:

John Morehart served briefly at the age of 55 with the Ohio Militia in the War of 1812.  He served from 13 October to 27 October 1813, in Ensign Peyter Huber's Co.  This company is listed on page 90 of the Roster of Ohio Soldiers in war of 1812, Clearfield Company, 1989.  On 3 Aug 1986, John Morehart's grave in Glick Church Cemetery was rededicated.  A Daughters of the American Revolution Revolutionary War marker and a Sons of the American Revolutionary War marker were placed on his grave. John was born in the Pennsylvania Dutch region of south eastern Pennsylvania in 1758 and died at the age of 56 in Fairfield County, Ohio, on 8 January 1815.  During the Revolutionary War, John was in his early twenties and served with Pennsylvanian Militia companies, made up primarily Pennsylvania Germans that fought British-backed Indians on the frontier.  After the war, he married Mary Alspach and they had eleven children.  First ten were born in Pennsylvania and the last one was born in Ohio.  In 1805 John and Mary moved their family from Northampton county, Pennsylvania to Fairfield County, Ohio.  The reason they moved to Ohio was that John was given a Revolutionary War land grant near Old Rock Mill in Fairfield County.  John Morehart's primary occupation was farming, at the time of his death, he owned 320 acres of land in section 28, Township 14, Range 20, near Greencastle, Ohio.  He died without a will and his estate is listed in Volume I, pages 27 to 29, DISTRIBUTION OF ESTATES, FAIRFIELD COUNTY, OHIO. John Morehart's Revolutionary War Service Pennsylvania Archives   Series Volume Page John Van Etten's Company 2 14 596 Ranger 3 23 297 Continental Line 5  4 336 Continental Line 5  4 660 Henry Keit's Co.  5  8  39 John Jacoby's Co. 5  8  67 Lewis Stacker's Co. 5  8 608 Philip Shrawder's Co. 5  8 618 On 11 Sept 1780 John was fortunate to be one of the Sugar Loaf Massacres survivors at Buck's Mountain where he "lost his rifle," but saved his "accouterments" during the battle on 11 Sept 1780.