The name Thomasite was derived from the transport vessel USAT Thomas (earlier known as SS Minnewaska in private service), which brought the educators to the shores of Manila Bay.
Established on January 15, 1904, the municipality was named after the first president of the United States, George Washington, as a tribute to the Thomasites, a group of American teachers who in the early 1900s established a new public education system in the Philippines, taught basic education, and trained Filipino teachers with English as medium of instruction.