Applying a scale to the map makes it look like "1 unit" is about 7.5 on the scale and the distance between Chicago and New York is about 10.8 on the scale.
In miles, the approximate straight-line distance from Chicago to New York on this map will satisfy the proportion ...
10.8/7.5 = (distance)/(557 miles)
(557 miles)*(10.8/7.5) = distance = 802.08 miles
The distance from Chicago to New York is estimated to be 802 miles.
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We note that the projection of the map is such that measuring distance in a straight line does not make any sense. We also note that the distance is on the order of 10% higher than the corresponding distance on Google Maps.