Thompson Center started selling the Hawken model in 1970.
The company and their Hawken model was one of, if not "the" leader in popularizing muzzleloading with the general public in the US.
This was 2 years after the GCA '68 passed which basically stopped people from buying firearms thru the mail.
Muzzleloaders were always exempted from this which led to a wild upsurge in the popularity of muzzleloading.
During this time there were dozens if not hundreds of companies in the US importing muzzleloaders from overseas but Thompson Center was one of the few companies that produced and sold a US made muzzleloading rifle here.