Sion Hill includes estates 22 & 23 in St. Croix’s Queen’s Quarter. Based on appearances on historic maps, the windmill was likely built in the 1750s in estate 23. The inscription on the main entrance keystone says 1757, a potential construction date. The windmill tower is in good condition.
The 1750 map indicates sugar cultivation and an animal mill near the border between estates 22 & 23. The first Beck printing had an animal mill in estate 23 but the second printing rubbed it out, replacing it with a windmill in estate 22.
The 1799 Oxholm map shows a windmill at Sion Hill on the border between estates 22 &23. The 1856 Parsons map shows a windmill at elevation 332 feet. All the 20th-century topographic maps show a structure identifiable as a windmill at Sion Hill close to the border between estates 22 & 23.
The 1750 map attributes ownership to the Reformed Church for estates 22 & 23. The maps from 1766 to 1791 attribute ownership of estates 22 & 23 to Bradshaw.
McGuire geographic dictionary of the Virgin Islands (p.178) provides location and early ownership information.