^^^ At least two of them came from mail order. theturtlesource.com sends half-dollar sized or larger turtles through the mail. They arrive in a small box ready to go. I recommend them.
http://theturtlesource.com/i.asp?id=100200300&p=Red-Eared-Slider-for-sale
A couple of the others were purchased from Petco.
All of them were juvenile size (half dollar) when I obtained them. The largest one is now as big as a dinner plate.
I tried to keep turtles found in the wild/road...doesn't work. They will die before they give up trying to escape.