I emailed Legacy to ask if they do their own cast, this was the response.

Thank you for the question.

At this time we do not make the cast iron in house. We get them from several companies all based in the US.

We have plans on opening a Casting Facility in 2018 and we will be doing our own castings in house then.

I hope this answered your question and if you have any more don't hesitate to ask

Thank You,
Legacy Cast Iron