It's on West Front Street dude...
https://maps.google.com/maps?q=casey%27s+buffalo+IA&ll=41.456301,-90.71866&spn=0.01256,0.021501&oe=utf-8&client=firefox-a&fb=1&gl=us&hq=casey%27s&hnear=0x87e3cfa4f910267f:0xafcb51eba9355d38,Buffalo,+IA&cid=0,0,4533138853134476542&t=h&z=16&iwloc=A