In less than two decades, SpaceX went from Elon Musk's dream of a greenhouse experiment on Mars to conducting the majority of U.S. rocket launches.

The early years of SpaceX reveal a company that teetered on the edge of dying out, as Musk has said. After three unsuccessful attempts to reach orbit, his team scrounged together enough parts for a fourth rocket, and SpaceX made history with its Falcon 1 rocket.

While Musk provided the vision, his company was not an overnight success. Key people, such as employees like now President and COO Gwynne Shotwell and investors like the members of the Founders Fund, helped forge SpaceX into the business it is today. SpaceX has won billions of dollars in NASA and Air Force launch contracts. It also carries payloads for private companies.

Now SpaceX is valued at over $30 billion and has more than 6,000 employees around the country. The company is launching rapidly, with a backlog of orders for its Falcon 9 and Falcon Heavy rockets. SpaceX is facing its greatest challenge yet in 2019: Launching astronauts for NASA. If Musk's long-term goal of sending humans to Mars is going to be realized, SpaceX must be able to regularly and safely launch astronauts into orbit.

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What SpaceX Means For Elon Musk's Mars Dreams