Windham is a Maine Co. And you could have an old Bushy marked from Maine as well if that does it for you.
Black Hole Weaponry, Oregon…
Made in Oklahoma firearms makes lower receivers in OKC
Mohawk Armory in Tennessee.
ETA: Anderson in Kentucky
Del-ton is in Elizabethtown NC
JD Machine Tech, Inc. - San Diego, California. Yea I know hard to believe AR lowers/uppers are being made in such and 2A unfriendly state.