Having covered E North Street, Eastern Avenue N, and Western Avenue, we now come to S Southern Street! This street originated in the 1891 plat of River Park, filed by Alexander Prentice (1820–1909) and his wife, Jane Thomson Prentice (1823–1911). It appears to be so named simply because it is the southernmost street in the plat, half a block north of the 1890 plat of South Park.
S Southern Street begins just east of 12th Avenue S on the west bank of the Duwamish Waterway, and goes ½ a mile to just west of 7th Avenue S, where it is blocked by Washington State Route 99 (W Marginal Way S). (Its first tenth of a mile is within unincorporated King County as part of the “Sliver by the River.”) It begins again in West Seattle as SW Southern Street at 35th Avenue SW, and goes ⅗ of a mile to 44th Avenue SW.