There are two reasons travelers can legally possess a valid second U.S. passport: One is political, the other is logistical.
First, politics. The U.S. government will grant you passport number two if you can prove that you鈥檒l be traveling between two countries that will deny you entry because you鈥檝e visited the other. The 鈥檚 official language does not pinpoint specific nations, but this听currently applies only to the Middle East, where many countries deny entrance to travelers who have an Israeli passport stamp. (Israel now lets travelers听听and instead receive a stamped piece of paper to keep inside the passport; still, the State Department will consider giving you a second passport if you鈥檙e visiting this region.)
The logistical reason is a little less straightforward but is one that all serious jet-setters should know. The will OK your second passport if you sent your original away to get a visa for one country听but are planning to travel to another in the interim. For example, say you鈥檙e going to Belgium, where no visa is necessary, but then plan to go , one of 41 countries with a visa program that听requires听you to send your passport in the mail to one of its consulates听or drop it off in person. (Brazil, China, and Russia are the other main tourist destinations on the list.) If your trip to Belgium falls within the听window of time you鈥檒l be without your passport鈥攁nd it can be held up for weeks or even months鈥攜ou will have no way of passing through EU immigration. A second U.S. passport is the State Department鈥檚 work-around.
The application process for a second passport is identical to the original, except you鈥檒l have to you fall into one of the aforementioned categories.听The second passport comes with its own unique number, is valid for two years (instead of ten), and can be听听just like your primary passport. It costs the same $170 fee as your first passport. Plan on for the process unless you use a passport concierge to speed things along.
听