There is some debate about whether there were two memorials or just one. All scholars agree that there was a set of memorial stones set up at Gilgal (the place where Israel camped). However, not all scholars agree that there were also stones set up in the Jordan River itself. Those who think only one set of stones is in view interpret Joshua 4:9 as referring to the twelve men taking the stones from the place where the priests had stood.1
9 And Joshua set up twelve stones in the midst of the Jordan, in the place where the feet of the priests bearing the ark of the covenant had stood; and they are there to this day.