You can enter the US through over 300 Ports-of-Entry (POE). A POE is any station: land, air or water, through which a person can enter the US. Immigration officials inspect all persons entering the US at a port-of-entry. At the port of entry, an official must authorize the visitor’s admission to the U.S. At that time Form I-94, Record of Arrival/Departure, which notes the length of stay permitted, is stamped. Those visitors who wish to stay beyond the time indicated on Form I-94 must contact the USCIS to request Form I-539, Application to Extend Status. The decision to grant or deny a request for extension of stay is made solely by the USCIS.