Nancy, I may be able to point you in the right direction. The name McPadden was apparently fairly unique in the mid-1800s to one civil parish named Innishmagrath in County Leitrim, which is also known as Drumkeeran. There is a chat group focusing on this area called drumkeeranfolk, found at egroups.com, with a wealth of information. If you can find the marriage certificate of your grandfather it should indicate what part of Ireland he came from (this is how I traced my grandfather), but it is likely that they came from Drumkeeran at some point. If James married in New York City, these records are available by mail or in person. I have several James McPaddens in my family tree, if you find out more, maybe there is a match. A number of my relatives settled in Bay Ridge. Good luck.