Threlkelds of Kirkoswald, Cumberland

I have been researching the history of the Threlkeld family, who lived in Kirkoswald, Cumberland, England. My great great grandmother was Elizabeth Threlkeld and she married William Fleming in around 1847 ( it is understood that they eloped). The Threlkelds were a large family and I believe that some of them emigrated to the USA but I have been unable to trace them from there. The history of this family goes back a long way - to Humphrey de Threlkeld in the 1300s