Somebody recently posted to the GENBRIT list that Hew Scott's "Fasti Ecclesiae Scoticanae; the succession of ministers in the Church of Scotland from The Reformation" has been digitized and posted to archive.org. Published in several volumes starting in 1915, the "Fasti" is the go-to compilation of Presbyterian ministers through mid-19th century, and includes a number of ministers who emigrated to North America. archive.org provides several ways of accessing the material, including reading it online and downloading a version readable on your computer or tablet.

http://www.archive.org/search.php?query=creator%3A%22Scott%2...

A bit more background:

http://en.wikipedia.org/wiki/Fasti_Ecclesiae_Scoticanae