Here is an interesting discussion;
http://blackpowdersmoke.com/revolvers/index.php?topic=25.0
There were only three American manufacturers of replica revolvers that did not use any Italian parts.
The first was L.A. Jensen in Lake City, FL, who produced a replica Spiller & Burr in the 1950's. He produced it in .44cal. in order to not be confused with the original. These were of excellent quality. Many were sold as cased sets. Only five of these revolvers have surfaced to date.
The second was Witloe Precision Inc. in Collingdale, PA, who produced the Remington New Model Army as the Grant Model and the Lee Model. The Grant Model had a steel frame and the Lee Model had a silicone bronze frame. These were the very first Remington New Model Army replicas manufactured by anyone. Witloe Precision Inc. discontinued making these revolvers after only two years because of the cheaper cost of the Italian revolvers. R. T. Lane of Poughkeepsie, N.Y. purchased the remaining inventory of partially assembled revolvers and parts. These revolvers are marked WITLOE COLLINGDALE, PA. in two lines on top of the barrel. Lane was given the right to only use the WITLOE name since Witloe Precision Inc. was still in business with government contracts. Because of the exceptional quality of the revolvers, R. T. Lane targeted the competitive shooter as his market, so most "2nd Generation" Witloes have target sights. So far only twenty 1st & 2nd Generation Witloes have surfaced.
The third was the 1860 Army that was produced by Firearms Specialties in Michigan. This was in around 1959 just when William B. Edwards was setting the ground work for the Centennial 1860 Army to be manufactured in Belgium. Only one of these revolvers has surfaced. It bears the serial number 7. See a discussion here about the Centennial 1860 Colt
http://www.thehighroad.org/showthread.php?t=729848&highlight=Centaur
All three of these pioneer American Companies met their demise because they could not compete with the prices of the Italian manufactured revolvers.