Most routers will only get about 300 ft. with a strong signal. I have one raching 700 ft. (over open ground) but extremely weak signal.
The "N" protocol is still in developement and if any hardware not of "N" protocol is used the whole thing reverts back to the lowest setting being used....."B" or "G".
I have been in touch with this company and they have helped me set up a wireless network out in the middle of no where. Very reasonably priced ! They have some hardware that is capable of the 1500 ft that you need to reach! Meraki infrastructure is your complete solution for deploying wireless networks of any size.