After the terrorist attacks on September 11, 2001, Congress legislated that all countries participating in the Visa Waiver Program-which lets foreigners visit without obtaining a Visa-must issue electronic passports. This led to international agreements and standards for epassports that are now in place.
Today, the United States and the 35 Visa Waiver Program countries are issuing epassports. Most other nations are in various stages of implementing a transition to epassports.
More information is available on the Department of State's Visa Waiver Program Web page