Here’s the herd of Y Combinator unicorns that DoorDash just joined

As the first of Y Combinator’s “unicorns” prepares to go public, a new one was born this week after DoorDash Inc. was the latest beneficiary of a SoftBank-led mega-funding round.

San Francisco-based Dropbox Inc., meanwhile, will likely be the first company from the Mountain View accelerator program to test its valuation on Wall Street.

The only other companies to hit a valuation of around $1 billion came through the sale of Twitch to Amazon.com in 2014 and the sale of Cruise Automation to General…