1.  LDS.  Family Search: Internet Genealogy Service:  IGI - International Genealogical Index (online at FamilySearch.org).

David MARSH Spouse: Nancy BOSLEY Marriage: 15 Jan 1791, Baltimore, Maryland Source: Maryland Marriages, 1777-1804. Maryland Historical Society

2.  1800

3.  1810

4.  1820 Census Index/Images (online at Ancestry.com; Image #15 of 37; extracted by Diana Gale Matthiesen):¤

1820

MD

Baltimore Co.

Dist. 2

Roll M33-41

p. 229

Ln. 15

David Marsh

200001-00001-0-100

These data indicate:

No. & Sex	Age Class	Therefore Born	Individuals Inferred
2 males	9 or under	1810-1820	= ? = ?
1 male	45 or over	in or bef. 1775	= David
1 female	45 or over	in or bef. 1775	= Nancy
1	person engaged in agriculture

It's odd that they have only two young children.  Did they lose all their previous children?  Are these grandchildren?  Orphans taken in?