If you are a citizen of a Visa Waiver Program (VWP) country, you must have a valid ESTA authorization even when transiting through the United States, as all travelers are required to go through U.S. immigration procedures upon entry.
When completing the ESTA application form, you must select “Yes” to the question “Are you transiting through the United States to another country?” before submitting your application.
*If you are not from a Visa Waiver Program (VWP) country, you must apply for a visa appropriate for your travel purpose.