Final answer:
The statement that Philadelphia, Pittsburgh, and Erie are first-class cities is false. Only Philadelphia qualifies as a first-class city based on Pennsylvania's classification system, while Pittsburgh is a second-class city, and Erie is a third-class city.
Step-by-step explanation:
The statement "Philadelphia, Pittsburgh, and Erie are first-class cities." is false. In the Commonwealth of Pennsylvania, the designation of a city's class is determined by population criteria set by state law. Philadelphia is Pennsylvania's only first-class city due to its large population. Pittsburgh is classified as a second-class city, and Erie is considered a third-class city. The classification system in Pennsylvania has three classes for cities, with the first-class designation reserved for cities with a population of 1 million or more. Pittsburgh, while historically significant in the American Manufacturing Belt due to its steel industry, does not have the population to qualify as a first-class city, and Erie's population is smaller still, further solidifying its third-class status. Additionally, it is worth clarifying that Pennsylvania did not adopt one of the most conservative constitutions of the Revolutionary Era; rather, its 1776 constitution was considered one of the most progressive for that time.