Chester County, Pennsylvania, has a recorder of deed records search here.
This is what is said on the site:
The information available via our online Eagle Web Records Search includes our verified document data from 1960 to the present, as well as associated document images from January 1994 to the present (see the current proof date at bottom left). Earlier index data is not verified nor complete. Subdivision plans are available from 1905 to the present.
Hat tip from a NEHGS newsletter.