<p>I’m sure that at some point along the way the park system in Philadelphia was the world’s largest municipal system. But the list I posted has two municipal parks in Phoenix with about 23,600 acres (and there’s another 16,000 acres in Scottsdale that is contiguous with a 7,500-acre Phoenix park), a single municipal park in Houston that is bigger than the whole Philadelphia system (who knew?), plus a county (county?) park half a mile away that is by itself almost twice as big as the main Fairmount Park. And those are the two cities closest to Philadelphia in size and population. Portland OR, less than half of Philly’s size, has about 11,000 park acres in its park system. I couldn’t find numbers on Los Angeles, but it clearly has much more park space than Philly, split between municipal and state parks (and LA has its patchwork of unincorporated municipalities to confuse things).</p>
<p>One relevant difference is that all of the Fairmount Park system in Philadelphia had to be purchased and contributed to the park. It was mostly developed in the 18th Century, and it is still dotted with mansions (and, as I said, the ruins of old mills along the Wissahickon and Cresheim Creeks). I don’t know about Houston, but the parks in Phoenix, Portland, and LA were pretty clearly never settled.</p>