David Karp created Tumblr sold to Yahoo for $1.1 billion.

At age 16, Karp was already a product manager at UrbanBaby, an Internet forum for parents. He had dropped out of Bronx Science high school a year earlier in 2001 to be home schooled, and never obtained a high school diploma.

From there, he started Davidville where he built the beginnings of Tumblr. That quickly became his full-time focus, and the company became the United States' ninth most visited website. In May, 2013, Yahoo bought Tumblr for $1.1 billion and put $81 million into Karp's pocket with the deal.