Illegal Immigration. The United States is a free and prosperous society with more than
5,000 miles of borders (2,000 with Mexico) and hundreds of international air- and seaports.
In theory a sovereign nation should be able to maintain secure borders, but in practice the
United States has been unwilling and unable to do so. Estimates of illegal immigration vary
wildly, from the official U.S. government estimate of 400,000 per year (about 45 percent of
the legal immigration), to unofficial estimates ranging up to 4 million per year The government
estimates that about 4 million illegal immigrants currently reside in the United States;
unofficial estimates range up to 15 million or more. Many illegal immigrants slip across U.S.
borders or enter ports with false documentation, while many more overstay tourist or student
visas.