On August 14, 1845 Thomas W. Starr of Philadelphia received U.S. Patent no. 4130 for Improvement in Preparing Matrices for Type by the Electrotyping Process.
"Electrotyping, that is the growing of a copper shell from an impression of typeset matter, which could be backed up with metal and used to print from as a substitute for cast stereotype plates, was invented in about 1840 and spread rapidly in the printing trade. The use of electrotyping to make matrices from cast type was the subject of US Patent 4130 of 1845, granted to Thomas Starr. By the 1850s, the electrotyping of matrices had entered the normal practice of typefounders. Increasingly, later in the century, punchcutters turned from cutting their designs in steel – especially the more elaborate ones – towards making them in typemetal, from which electrotyped matrices could be grown" (http://typefoundry.blogspot.com/2009/01/recasting-caslon-old-face.html, accessed 10-10-2011).
Starr's patent was unusually brief, only one image and one page of text. I have reproduced them both here.
Printing and the Mind of Man. Catalogue of the Exhibitions at The British Museum and at Earls Court London (1963) no. 17.