They kept evolving during centuries. In French cities for example they destroyed the small alleys to make big roads for cars, and in more recent years we're back to giving priority to pedestrian, bikes and public transportation.
But in the case of Chicago, nobody really lived there until recently. I'd bet that in the last thousand years or more, there were never more than 500 people living in the general area until 1820 or so. The first Europeans in the area were the French, who saw it as an amazingly good logistics hub for shipping between New Orleans and their settlements in what is now Quebec. But they had no real interest in living in Chicago any more than Native Americans - up until the "Raising of Chicago", it was a pretty terrible place to live!
If you are in Chicago and come across a road that is not on a grid with intersections at 90 degree angles, there is a fairly good chance that it is centuries-old Native American path. For example, Milwaukee Ave was a path that led to (what is now) Milwaukee, Michigan City Road was a path that led to (what is now) Michigan City (where it met up with the path that went from (what is now) Detroit to (what is now) Rock Island Illinois on the Mississippi River).
Very cool.
This relates to the fact (and I think this is what the parent poster is referring to) that these cities started way before any cars or bikes existed, so cities had to work for pedestrians.
Hmmm. I disagree. In (continental) Europe the historical city centres are still the place where people live. Business areas have generally been built outside the historical part, except for the case where inner cities where destroyed in WW2. Maybe that's what you meant?
Old cities started as settlements, which more and more people moved to. Those people considered things like walking distance. Maybe they "designed" the places to put their homes, but the thing as a whole was in many cases not planned-through.
And even with the cities that were, pedestrian comfort was the main (or one of the main) concern(s).