(at around 31 mins) In the alien followers camp, there's a woman looking through a telescope. This is a Newton telescope, which is a hollow tube with a concave mirror at one end. The eyepiece is located close to the open end of the tube, so the telescope shown is actually pointing downwards towards the ground. The six screws that can be seen in the "opening" of the tube that is pointing towards the sky are in fact the concave mirror mount and adjustment screws.
When Sam and Dean follow Mr. Brennan to his house from the store; Mr. Brennan is seen unloading his car. We see that there is one box left in the car as Mr. Brennan returns from his house. The scene cuts to Mr. Brennan closing his now empty car.
When Sam and Dean first visit Mr. Brennan, the outside window of his workshop says Carthage.