On November 10, 1951, Mayor M. Leslie Downing of Englewood, New Jersey, picked up a phone and dialed 10 digits. After 18 seconds he connected with Mayor Frank Osborne in Alameda, California. It was a milestone moment in the history of the telephone—even though the first phone call had been made 75 years earlier. Why? Because it marked the end of the “number please” operator and the beginning of quicker, cheaper connections.

Making history doesn’t always mean taking a giant leap forward. The path from semaphore to telegraph to telephone to email is made up of incremental steps that improve quality, make life easier, and pave the way for the next innovation.

Google took one such step on April 1, 2004, when it launched Gmail. Other companies had provided free Web mail services for years, but Google’s improvements to the speed and usability of the service helped it quickly become an industry leader—supplanting many software email clients in the process. As Wired magazine reports, its interface “was fast and elegant just like a desktop app.” It managed this feat through the use of Ajax, a programming technique that allowed pages to update sections of their content on the fly. And the extra storage—more than a hundred times the size of its competitors—didn’t hurt either.

Today, Ajax has become a standard component of every Web mail service, and imagining a world without slick, Web-based email access is just as difficult as imagining a world in which we still used operators to call cross-country. As technology evolves, each milestone quickly fades into the background of the next new thing. Only five years old, Gmail’s status as one of those milestones is undeniable. Happy Birthday, Gmail!