I have read that, and until recently assumed that, S Horton Street is named for Dexter Horton (1825–1904), but have come to wonder if it instead is named for Julius, his younger brother (1834–1904), or for the Horton family in general. Julius came to Seattle in 1869, bought land in South Seattle in 1871, and platted Georgetown in 1890, naming it after his son, George (1865–1927), who had recently become a doctor. (Georgetown became a city in 1904 and was annexed by Seattle in 1910.) S Horton Street doesn’t run through Georgetown — it’s around 2 miles north of there — but it does run through South Seattle. It appears to have been named in 1870, after Julius arrived in town but before he bought what is now Georgetown. I am not sure if Dexter had any special connection to South Seattle; he certainly never lived there.
S Horton Street begins at E Marginal Way S and goes ⅔ of a mile east to 6th Avenue S, with a brief interruption at the SODO Busway. After a block-long segment between Airport Way S and 10th Avenue S just west of Interstate 5, it resumes on Beacon Hill at 13th Avenue S, where it goes one block east. It begins again at 16th Avenue S and goes ⅖ of a mile to 23rd Avenue S, being a stairway and pathway from just east of 19th Avenue S to 20th Avenue S. Horton resumes east of Kimball Elementary School at 24th Avenue S and goes a block and a half before it ends at the Cheasty Natural Area. Besides a very short segment just west of Martin Luther King Jr. Way S, its next appearance is at 33rd Avenue S and S Walden Street. From here, it goes ½ a mile east to Lake Washington Boulevard S, being a stairway between 36th Avenue S and 37th Place S and a stairway and pathway between Cascadia Avenue S and Sierra Drive S. Between Sierra Drive S and Lake Washington Boulevard S, it is part of Landing Parkway, under the jurisdiction of the parks department.