The elevation is 118 feet above sea level. According to the United States Census Bureau, the CDP has a total area of 2.3 mi² (5.9 km²), all land.
Machias is located at 47°59′51″N 122°2′50″W (47.997610, -122.047196).
Machias was laid out in 1888, and named after Machias, Maine, the ancestral home of a first settler. A post office called Machias was established in 1892, and remained in operation until 1943.