Chicago, IL

TechNexus was founded in Chicago in 2007, although the exact date is a bit fuzzy.
You see, they started as an informal gathering place for technologists from a variety of industries and company types. These were the days before many workspaces existed to facilitate such get-togethers; they did it because we were entrepreneurs ourselves, and it just made sense to help people get together for a few beers, and share their ideas about fixing problems and grabbing opportunities.

Eventually, over 200 companies were born or grew there, raising $225 million while on the floor and creating thousands of paying jobs. A new industry of tech-focused companies emerged in Illinois, so they created an association to represent them — the Illinois Technology Association — which now boasts 700 members.