I have been told on good authority that the following families came to St. Croix from County Fermangh Ireland, beginning in the early 1830's: Balfour, Fleming, Patterson, and Latimer. County Fermangh borders County Cavan on the northwest, so this adds to the families previously identified as arriving from that region
(see
http://maxpages.com/irishcrucians).
We might be able to narrow things even more, for some indications suggest a clustering in the Frederiksted area of County Cavan immigrants. Tramping through the Frederiksted Cemetery recently, I came across a monument for John McCabe ("native of Co. Cavan Ireland who died 11 Oct 1890, aged 66 [erected by his nephew Patrick Brady]"); a pair of tombstones for Gaffneys ("Thomas, born Aug 7 1871, Co. Cavan, Eire, died Sept. 8 1939, St. Croix"; and "Ellen, nee Gallagher, born June 4, 1873, Co. Cavan, Eire, died Oct. 16. 1947, St. Croix"); and tombstones for Farrellys ("Mary E. 1888 - 1937" and "Patrick A. 1877 - 1951"), a family known from other sources to have come from County Cavan. Others buried in Frederiksted Cemetery include Hewitts: John ("b. Ireland - d. St. Croix 9 Dec 1895; 51 yrs." and Robert ("b. Ireland - d. St. Croix 11 Aug 1899; 38 yrs") and John T. Armstrong ("22 Jan 1911 - age 52 yrs"). Again, there is evidence that both the Hewitts and Armstrongs were from County Cavan.
Was 19th century Frederiksted a center for County Cavan arrivals? Curiously, I came across no graves on which the person was said to have come from some other county in Ireland; although I could well have missed some. If nothing else, the graves of John McCabe and the Gaffneys suggest that being born in County Cavan was regarded as noteworthy.