In the 1850 Agriculture Census for Maryland (1), Henry Hays is listed as owning 80 improved acres and 20 unimproved acres.
In the Washington County Circuit Court records in the Maryland State Archives (2), Henry Hays has 4 personal land transactions that occurred before 1850 and one last transaction in 1854. From copies of the county records that genealogist Bob Fout found in March 2011, I can see the details of those transactions.
1843, Henry Hays bought 83 acres from John D & A Eakle (3)
1844, Henry Hays & wife sold 6.5 acres to Martin Lyne (4)
1847, Henry Hays & wife sold 12.75 acres to Martin Line (refiled in 1848) (5&6)
1850, Henry Hays bought 7.25 acres from George Strause & wife (7)
Henry Hays has around 30 acres more attributed to him in the 1850 census than can be accounted for in these transaction descriptions. Since the description of the land records index indicates the index covers records from 1777, there may still be other non-indexed transactions to find or he may have inherited land.
Sources:
(1) U.S. CENSUS BUREAU (Census Record, Maryland) Agriculture, Washington-Worcester, 1850, MSA SM61-152, M 3018-2, entry for Henry Hays, pp.591-592, line 32. digital image (http://msa.maryland.gov/megafile/msa/stagserm/sm1/sm61/000100/000152/pdf/msa_sm61_000152.pdf: accessed 18 Sep 2015)
(2) WASHINGTON COUNTY CIRCUIT COURT (Land Records, Index, Original) Ha, MSA CE17 12. digital image (http://msa.maryland.gov/megafile/msa/coagsere/ce1/ce17/000000/000012/public/ce17-000012.pdf; accessed 21 Sep 2015) entries for Hay, Hayes, Hays, pp.163-170
(3) WASHINGTON COUNTY CIRCUIT COURT (Land Records) Liber: OHW1; Folio: 308; MSA CM1130-44; CR34152. microfilm Deed: Henry Hays from John D & Amos Eakle, June 17, 1843.
(4) WASHINGTON COUNTY CIRCUIT COURT (Land Records) Liber: OHW2; Folio: 593; MSA CM1130-45; CR34153. microfilm Deed: Henry Hays & wife to Martin Lyne, December 27, 1844.
(5) WASHINGTON COUNTY CIRCUIT COURT (Land Records) Liber: IN2; Folio: 874; MSA CM1130-47; CR34155. microfilm Deed: Henry Hays & wife to Martin Line, November 5, 1847.
(6) WASHINGTON COUNTY CIRCUIT COURT (Land Records) Liber: IN3; Folio: 528; MSA CM1130-48; CR34156. microfilm Deed: Henry Hays & wife to Martin Line, May 27, 1847.
(7) WASHINGTON COUNTY CIRCUIT COURT (Land Records) Liber: IN5; Folio: 181; MSA CM1130-50; CR34158. microfilm Deed: Henry Hays & wife from George Strause & wife, June 5, 1850.