 The highway's interchange with I-405 in northern Bothell was opened to traffic in November 1969.Major suburban development in the Mill Creek area began in the 1970s and contributed to growing traffic congestion on SR 527, leading eventually to development moratoriums as temporary measures to quell growth.The northernmost section of the highway, in Everett between 112th Street and the Broadway Interchange, was expanded to five lanes in the late 1970s using city funding, while the rest remained two lanes wide.