Just call your local Goodwill and ask where there is one with an outlet. The 'outlet' is just a big back room behind a regular Goodwill where they dump the clothes. I think they give them a little time and then probably sell them by the bale, to overseas. I know another charity store in town does that. They put hardly any clothes out in their store but bale up most of what's donated into a huge bale like cotton used to be baled into... tons, in weight! Then they ship overseas and make their money that way.
By the time they turn over the unsold clothes, more are ready to be dumped into the outlet bins. Stuff is constantly being donated. People are pretty fickle with their wardrobes!
I had shopped at this Goodwill before, never knowing it had an outlet in the back!
Tonight I'm cutting up shirts (after washing them) and realize that for the quilt I want to make I need a lot more red shirts than I have. Probably more blue, too. So I may have to go and buy shirts in the regular thrift stores. There is one more Goodwill with an outlet in our area (Jackson). Givio, they are 45 minutes away from me, too... both of them, in different directions. Ours closes at 2pm, so if you find one be sure to go early, just in case.