Park City is an old mining town (and one of the few towns in Utah established by non-Mormons). You're right that there is more frame construction than brick. Most of the historic structures were frame rather than brick (at least the residential ones), and they were put up quickly. The elevation change on Main Street made for additional challenges. As an interesting historic note, the Great Fire of 1898 destroyed 200 of the 350 structures, homes, and businesses on Main Street, but most were rebuilt within 18 months.

If you're really interested , this document has some fascinating historical background as well as the current guidelines for construction in Park City's historic districts. It includes a description of the architectural character of Historic Park City. I love the old photos they've included.

And thus concludes the history and architecture lesson for today.