In 1870-72, John Marius Wilson's Imperial Gazetteer of England and Wales described Earldoms like this:
EARLDOMS, an extra-parochial tract in Alderbury district, Wilts; 7½ miles SE of Salisbury. Pop., 48. Houses, 9. It was an ancient property of the Pembrokes; is much occupied with dense wood; and has, among its wood, an anciently entrenched hill, with single rampart and ditch.
A Vision of Britain through Time includes a large library of local statistics for administrative units. For the best overall sense of how the area containing Earldoms has changed, please see our redistricted information for the modern district of Salisbury. More detailed statistical data are available under Units and statistics, which includes both administrative units covering Earldoms and units named after it.
GB Historical GIS / University of Portsmouth, History of Earldoms, in Salisbury and Wiltshire | Map and description, A Vision of Britain through Time.
Date accessed: 30th November 2015
Click here for more detailed advice on finding places within A Vision of Britain through Time, and maybe some references to other places called "Earldoms".