Half the USA for SALE!

It is the year 4115, and the Earth government is under pressure; to maintain peace with the intergalactic neighbors over a deal that recently ended sour, they need to offer a half of what used to be known as the United States of America to a government team of investors from the nearby galaxy.

If they don't make a reasonable offer, specially after the recent blunder which forced them into this situation to begin with, a fierce war would be a real possibility - one that the Earthlings would want to avoid almost at all cost.

They don't want to solely decide which half of the the USA to sell, as they fear that if in time, these fierce investors feel that they've been taken for a ride (weather they have or haven't in reality is not even an issue), they may react in a damaging way.

They also don't want to offer more than a fair share for a couple of reasons - firstly, they're humans and naturally greedy, and would much rather minimize their losses, and secondly they don't want to appear weak and desperate (any more than they already have).

In other words, they need to slice the country in to two, fair slices.

Fairness in not purely in real-estate terms, but also factors in aspects of the land such as the weather, pollution levels, mineral resources, crime-rate, properties, etc.

As a side-note, it's also worth noting that what is worth one thing to the humans, is not necessarily worth the same to the investors, and vise versa.

What's the most elegant solution that the humans can offer, which will guarantee maximized satisfaction on both sides.

Note that while the aliens are fierce, they are still logical and would not wage a war if they can't logically prove that they've been wrongly done by.