If you walk down any busy street in America, you will probably see many people with their hands up to their ears. Others may be pushing buttons on a small electronic device in their hands. Talking or sending text messages on mobile phones has become an important part of American life.

Until nineteen seventy-three, most telephone calls were made either at home, at a business or in a vehicle. But on April third of that year, Martin Cooper of the Motorola Company made history. While walking down the street in New York City, he made the first mobile telephone call.

Mr. Cooper had helped invent the DynaTAC 8000X. It was a mobile, or cellular, telephone often called "the brick." It was much larger and heavier than the mobile phones we use today. After that first call, it took ten years before the phone was ready to be sold to the public. The first ones were very expensive. They cost almost four thousand dollars each. But even with that size and cost, many people stood in line to buy them.

The first mobile telephones used a system, or network, called 1G. It was the "first generation" of technology. This allowed one person to call and talk to another person, but that was all. By the early nineteen nineties, the second generation, or 2G network, came into use. It allowed talking and sending text messages. By that time, cell phones were much smaller and cost much less.

In two thousand one, the first 3G systems were being used. This new network permitted people using cell phones to make calls, send text messages and use the Internet. Users could even keep photographs and music on their phones, and send them to their friends.