The passport hasn't always been as crucial to international travel as it is today. Granted, in earlier times, people had fewer borders to cross than they do today, but doing so was much less of a hassle.
Passports, in the form of official travel documents, have been around since biblical times, but it was in the 15th century that the first true passport was born, at the behest of Henry V, of England. The document was designed to identify its holder as English wherever he or she traveled and was one means to obtain passage into a walled city while travelling abroad. In fact, many scholars believe that the word "passport" refers to the "porte," or doorway, in city walls. Henry's passport differed from earlier examples, which merely listed cities that a traveler could enter.
The modern passport could not have developed without both the emergence of social science and the rise of nationalism and breakdown of the European system. By the end of the 19th century, nations had begun to understand citizenship in a robust, participatory way, and passports became a means by which to classify their citizenry and define them as part of the nation. It also served as a nifty means to keep tabs on skilled workers who traveled abroad. Social science, which during the 19th century developed a panoply of methods for classifying people based on physical type, made physical description based on indentifying features a requirement for a proper passport. Naturally, by the early 20th century, these descriptions would be supplemented by photographs of the passport holder.
Passport use was largely informal prior to World War I. With the war, nations began clamping down on cross-border movement in order to foil spies and keep out saboteurs. As the treaties that had bolstered the European system went up in flames, so too did the reciprocal rights of Europeans to travel across borders. By the end of the war, passports became required at all ports of entry in Europe, a practice that spread across the globe.
Don't worry if you don't understand how to get a US passport. When it comes to getting a passport, it's best to be prepared, plan ahead and stay organized, especially if you need an expedited passport. Damaged, incomplete or missing documents will land your application squarely on the rejection pile.
In 2007, the United States implemented a program which changed, significantly, the way in which Americans travel into and out of the United States.