There is some wonderful running at the eastern end of St. Croix. One good option is East End Rd., which goes for 1.5 miles from Cramer Park to Point Udall. You’re above the water here, and the water views are fantastic. Note that this road has no shoulder, so extra caution is needed. There’s also a killer hill at the 1.6 km mark that goes for 0.8 km with grades up to 10%. Add-On: There’s a spur trail off East End Rd. that leads to the Isaac Scenic Overview and Isaac Bay, mainly downhill. A bit narrow, but runnable.
There is also some of the USVI’s most accessible and scenic trail running here. The Jack Bay Trail comes off East End Rd. at the Observatory and leads to the Jack and Isaac Bay Preserve. It is 1.2 miles to Jack Beach. It’s a gravel trail, wide enough for running, with some loose rock — but runnable. Note that the first 1 km is a killer hill — 600 feet, up to 17% grade. At Jack Beach, there are trails that head west to Hughes Point (0.3 miles) or to Isaac Bay (0.7 miles). Or, it’s 1 mile between Hughes Point and Isaac Bay — and this section is flatter. At Hughes Point, Point Rd./Grape Tree Rd. goes for 0.5-1 miles along a very pleasant coastal section. Great views, some open and some tall grass.
Also some decent neighborhood running just south of East End Rd. in an area called ‘East End Quarters‘, for example Seven Flags Rd. or Tipperary Rd.