The product doesn't say where the mullein is sourced from, but the outer box states: it's a family owned and operated business; their "facility" (packaging plant?) is cGMP Certified; proudly based in the USA; and the outer box also states: Manufactured by Nature's Answer, 85 Commerce Drive, Hauppauge, NY 11788
You could Google maps that address and see if that's just an office or if it's a manufacturing facility.
FYI, I have been using this product for 4 or 5 years, and it really has work tremendously well for me. I give it my highest rating for a supplement that actually works. YMMV