From the Georgetown Law Library Blog we have the following:
Georgetown Law Library's Special Collections holds several legal history manuscript collections including the Lord Eldon Collection (Lord Eldon was Chancellor of Great Britain from 1801-1827), the Francis Caleb Brown Collection of bound manuscript English law reports from the 17th century and American Justice of the Peace writs from the late 18th and early 19th centuries, and the 13th & 14th Century English Land Grants Collection of vellum land transfer documents from the time of Edward I, as well as many other collections of documents and personal papers.
More.