That's the point of the article though: very few people needed to travel 300 miles in 1750. New York to DC is only 236 miles--the very first settlement in Chic

That's the point of the article though: very few people needed to travel 300 miles in 1750. New York to DC is only 236 miles--the very first settlement in Chicago was in 1780. The technology to travel longer distances more quickly (via e.g. railroads) is what led to the 'need' to travel 300 miles on a more regular basis. Before that the vast majority of people would be able to live their lives in a much smaller area, and representatives that 'needed' to go to DC would have the time and resources to spend the multiple days traveling for their congressional session. (In fact this is why congress is divided into sessions instead of legislating continuously as would be possible in modern times.)