From HousingWiki
Mowry, The California Progressives, 1951. From YIMBYwiki library

Progressivism is the support for or advocacy of social reform. As a philosophy is based on the Idea of Progress, which asserts that advancements in science, technology, economic development, and social organization are vital to the improvement of the human condition.  [see more on historical background in Wikipedia: Progresssivism]. 

Progressive Movement (United States)


Progressive Movement (California)

See also Wikipedia: California Progressive Party


Progressives (San Francisco)

see DeLeon & Latterman, PVI (Progressive Voter Index). 
Note: a play on the older and better-known Cook Partisan Voter Index, also referred to as PVI. 
because, special snowflake.