The digitized copy of this book is available free, online:

History of Delaware County, Pennsylvania

Originally published in 1862, it's fully searchable and indexed.

Go to http://books.google.com
Select/click "Full view books" and
Type in: history delaware county

(Note: If you don't click "full view", you’ll include books that show you just "snippets" of the text, not the whole text– which isn’t as useful!)

Click highlighted results to see full book.

The entire book can also be saved as your own pdf file!