If you’re visiting Amish Country in PA, don’t forget to leave time for Intercourse.
Or risk getting caught in Blue Ball? 
Thanks all.
So, the day’s plan of Independence Hall & Liberty Bell, walk to Elfreth’s Alley, then along Market to City Hall is walkable? Lunch at Reading Terminal. The only real time constraints is we get to Philly at 10 and I want to hear the Wanamaker Organ at 5:30.
Seriously, do drive thru it if you’re going to be out that way. It’s parallel to but not the congestion of the main drag Rt 30 / Lancaster Pk. Lots of rolling hills & farms (many w/o power lines obstructing your view) make for some very pretty views.
Yes, it’s walkable. Independence Hall to City Hall is ≈ 1 mile. Elfreth’s Alley adds a few blocks to this as it’s the opposite direction. Elfreth’s Alley is a residential street. While one of the houses is a museum, the rest are private residences. If you were to cut anything, this is what I recommend missing.
Why are you going to City Hall? To take a tour? There is both the tower tour & a more comprehensive 2-hour tour of the building. If you do the longer tour, there is some great architecture in that building. If you’re interested in the tower tour, there’s a much higher observation deck a few blocks west in One Liberty Place.
OTOH, if seeing the Wanamaker Organ is so important to you, you might be able to make arrangements for a tour beforehand. (I’ve done the super-inclusive private version - INCREDIBLE!)
While you’re in Pennsylvania, pick yourself up some raisin-filled cookies and birch beer.