"Hermitage" was a large parcel of land, parts of which are now called Aspen Hill, Maryland.
Hermitage lies entirely south of the tract of Bradford's Rest. The line of division between them runs almost exactly east to west, with the so-called "West line of Hermitage" running through Aspen Hill just south of the Aspen Hill Library.
In modern terms, Hermitage is bounded more or less from the Bradford's Rest Southwest Corner Marker Stone to Bel Pre Elementary School, south to the intersection of Georgia Avenue and Plyers Mill Road, northwest to roughly the intersection of Aspen Hill Road and Veirs Mill Road, and thence north along a line just east of Rock Creek, to the place of Beginning.
From The History Of Montgomery County, Maryland, From Its Earliest Settlement In 1650 to 1879 (Boyd, T. H. S.):
Hermitage. Granted to William Joseph, May 2nd. 1689, for three thousand eight hundred and sixty-six acres. This grant lies on the east side of Rock Creek and adjoins "Joseph's Park" on the north, and extending from Vier's Mill to the intersection of the Rockville and Washington Turnpike with the Union Turnpike Company's road. The Brookeville and Washington Turnpike passes through it from the Watery Branch to one-fourth of a mile south of Mitchell's Cross Roads. The City road, from Rockville to Washington passes through it, from Graves' farm to Aug. Burgdorf's farm, at the intersection of the Brookville and Washington Turnpike. The Norwood Turnpike traverses the tract from Kemp's store to Lyddane's farm, or its intersection with the Brookville and Washington Turnpike. It embraces many fine farms and elegant residences. Lying to the east of "Hermitage" is St. Winexburg..."
On May 10, 1864, one Charles H. Anderson received title to "the Hermitage" (Montgomery County Land Records E. B. P. 1 at folio 203 et seq.).
Anderson had got it from Julius S. Bohrer et al. in 1854 (J. G. H. 4, folio 63).
The original patent was from 1689, to one William Joseph, for some 3866 acres.
Additional well-researched history is available at the Discover Wheaton History Page. This will lend some clarity to the changing names of major roads and even towns in the last two centuries. It also gives some detail about the history and locations of land grants near to, but outside of Aspen Hill.
An interesting deed describing a property with bounds from both the Hermitage and from Bradford's Rest is in liber JLB 184 folio 162 of the Montgomery County Land Records, from Nicholas M and Mrs Bettie M Howes to George H Earle Jr, dated October 17, 1905, referencing liber 24 at folio 451. Equally interesting, though perhaps a bit outside of the bounds of Aspen Hill proper, a deed beginning a liber JLB 184 folio 163, where Mr Earle acquires a large tract of land from Bradford's Rest of property formerly belonging to Charles Abert.
The boundary between Hermitage and Bradford's Rest is often referred to in deeds as "the West line of Hermitage". It runs almost perfectly east to west, and is aligned almost exactly with the modern-day Aspen Hill Road as aligned just south of the Aspen Hill Library. Indeed, this boundary extends to the east beyond the bounds of Bradford's Rest, and is seen as the property line between the Gate of Heaven Cemetery and the Aspen Manor Shopping Center.
On September 7, 1922, Edward Palmer and Mrs Lottie Rabbitt sold a sizable swath of land to one Frank L. Hewitt (liber 320, folio 321), which is now Hewitt Avenue (and the surrounding lands) in Aspen Hill.
On April 25, 1907, the Rabbitts had bought this land as the result of a settlement (Equity case #2271, Alexander Rabbitt complainant, Edward Olin Garrett et al. defendants). On the same date, Edward Palmer Rabbitt also bought lands from Isaac Beall and Mr & Mrs Edmund D and Anna E Beall as a result of another equity settlement (#275) in a tract of land called "Bel Pre" (liber 192, folio 496-500).
Perhaps you would like to read the discussions on the Talk:Hermitage page?