NEW UNICORNS: The 42 startups that grew to be worth billions in 2015

REUTERS/Sean Gardner

2015 was a big year for private market tech companies and their valuations.

Uber, already the most valuable private tech company in the world, is rumored to be raising a new round of funding that would value the company around $60 billion.

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And this year alone, 70 startups became members of the "unicorn club," meaning new rounds of funding valued these companies at $1 billion or higher.

42 of those companies are US based, according to research analytics firm CB Insights. We've rounded those companies up and ranked them from least to most valuable.