He states that he was a member of Lincoln's Inn, and for some part of the reign of Charles I he was clerk of the peace for the county of York.
In this way he slowly accumulated a very extensive antiquarian miscellany in manuscript, which has been largely used by local historians and genealogists.
Hopkinson was well enough known and respected to have special letters of protection granted to him and his father during the civil war by both the Marquis of Newcastle and Fairfax.
Hopkinson's collections, which comprised at least eighty volumes, passed on his death to his sister Jane, who had married Richard Richardson.
About half came by descent into the possession of Frances Mary Richardson Currer [q. v.] of North Bierley and Eshton in Yorkshire, and from her passed to her relative, Sir Matthew Wilson.