The same with most of other countries, there are several types of journeys you can go through to visit the United States, namely by air, sea or land. Yet, no matter the type is, one thing that you certainly need to have is a visa. You can either use an ordinary US Visa or the one called as Visa Waiver Program and to use the latter, you need an Electronic System For Travel Authorization or ESTA.
For example, if you are entering the United States by land either from Canada or Mexico, the requested documentation is the same with using an ordinary US Visa. It means there is no requirement for a round-trip ticket and a signature of a freight service as if you travel to the country by air or by sea. However, you still have to be able to convince the inspecting officer that you have sufficient funds to cover yourself during your stay and to leave America.
If you want to visit the United State under the Visa Waiver Program with an (ESTA by the air or sea, you need to know that there are some qualifications that you have to be able to fulfill. The first qualification is that you have a round-trip ticket or onward journey. If traveling using an electronic ticket, a copy of the travel list must be kept for display to the immigration inspection officer. Travelers with a one-way ticket with the final destination of Mexico, Canada, Bermuda or the Caribbean Islands shall be permanent residents of the territory.
The next is that you have to enter the US by using air or water freight services that have agreed to participate in the program. This includes American airlines that have entered into an agreement with the Department of Home Security to transport passengers who use the Visa Waiver Program.