This street was established in 1926 as part of North Beach, an Addition to the City of Seattle. As the advertisement below indicates, the addition features excellent views of Puget Sound. I assume Neptune being the Roman god of the sea was the inspiration behind the name.
Born and raised in Seattle, Benjamin Donguk Lukoff had his interest in local history kindled at the age of six, when his father bought him settler granddaughter Sophie Frye Bass’s Pig-Tail Days in Old Seattle at the gift shop of the Museum of History and Industry. He studied English, Russian, and linguistics at the University of Washington, and went on to earn his master’s in English linguistics from University College London. His book of rephotography, Seattle Then and Now, was published in 2010. An updated version came out in 2015.