In the 1609 [[Plantation of Ulster]], Slieve Rushen formed part of lands which were granted to John Sandford of [[Castle Doe]], Co. Donegal by letters patent dated 7 July 1613 (Pat. 11 James I - LXXI - 38, ‘Slewrussell'). The grant basically included the top of the mountain only, as the townlands on the lower slopes had already been granted to other grantees in the Plantation, as appears on the 1609 Baronial maps and in later grants. The mountain was later sold by Sandford to his wife's uncle [[Toby Caulfeild, 1st Baron Caulfeild]], Master of the Ordnance and Caulfield had the sale confirmed by letters patent of 12 July 1620 (Pat. 19 James I. XI. 45 ‘Slewrussell'). Coincidentally the mountain was later part owned by John Sandford's daughter, Magdalen Gwyllym the wife of Thomas Gwyllym, the owner of the [[Ballyconnell]] estate.