In 2003, Odysseas Tsatalos and Stratis Karamanlakis, wanted to work together despite the distance between them (one in Greece, the other in the USA). They came up with oDesk.
It was a platform that helped companies connect with potential contractors and workers. At first, it was a staffing firm. The team would manually do all the matching between the companies and the potential employees. Then, it became a marketplace for remote work.
So how did oDesk get it's first users? They solved the chicken & an egg problem by figuring out on which group should they focus on first. They choosed the clients paying for the job to be done, because they would attract the freelancers. They bought ads on Techcrunch. Once they got the clients, they keep them for as long as they could.
Then with clients, they got a lot of freelancers - at that point, more than 5,000 per day, organically. They were coming because oDesk had the most jobs.
Later, oDesk got merged with Elance (a similar, but smaller platform). The Elance-oDesk merger got rebranded to Upwork. It was a completely new thing, but basically, Upwork was just a better oDesk. Upwork encouraged Elance users to move to the new platform by giving incentives. Soon, Elance got phased out entirely.
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