What is now Pacific Street was Harrison Avenue in the 1889 Latona Addition and Railroad Avenue in the 1890 Brooklyn Addition, corresponding to the eastern part of Northlake and to the University District, respectively. The road was built on either side of railroad tracks that were originally part of the independent Seattle, Lake Shore and Eastern Railway, but which were soon thereafter taken over by the Northern Pacific Railway. (The route of the SLS&E through and east of Seattle is now the Burke–Gilman Trail, the Sammamish River Trail, and the East Lake Sammamish Trail.)
In 1906, Harrison Avenue became Pacific Place and Railroad Avenue became Brintnall Place. (Why the opportunity wasn’t taken to match the names is unclear. Brintnall Place may have been named for Burgess W. Brintnall, who, according to the September 1912 issue of the Northwest Journal of Education, had been school superintendent for Olympia and Thurston County, founded the journal itself, and, after moving to Seattle in 1899, founded the Pacific Teachers Agency. He was murdered on July 3, 1912.)
At some point both streets became Pacific Street. Brintnall Place appears for the last time in The Seattle Times in October 1920, and Pacific Street for the first time in July 1921. The 1920 Kroll atlas shows all three names, including Pacific Place, indicating the change must have been planned at the time of its publication.
I haven’t seen any indication of why the Pacific name was chosen. Seattle got an Atlantic Street in 1895 — maybe it was thought the other major ocean deserved a street as well. But I wonder if it wasn’t named for the Northern Pacific, whose tracks the street ran along?
Today, NE Pacific Street begins at Montlake Boulevard NE, at the north end of the Montlake Bridge and the southeastern corner of the University of Washington campus, and goes ¾ of a mile to Eastlake Place NE, underneath the University Bridge, where it becomes NE Northlake Way. It begins again at NE 40th Street just west of the Ship Canal Bridge and goes another ¾ of a mile to N 34th Street just east of Meridian Avenue N.
Pacific Street’s current configuration is the result of a realignment that took place in the 1970s; originally, instead of turning west at University Way NE, it kept going northwest, cutting through what is now the University of Washington’s West Campus, and there was no interruption between the University and Ship Canal Bridges. The Burke–Gilman Trail follows the original railroad alignment, though, as does, for a few blocks, the campus road Cowlitz Road NE.