Windham is a Maine Co. And you could have an old Bushy marked from Maine as well if that does it for you.
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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.