This paper examines a relatively understudied sociolinguistic variable in English, the retraction of (str) (e.g., street pronunouced as shtreet), using a corpus of Philadelphia speakers spanning more than a century of apparent time. Using automated acoustic methods on naturalistic data allowed (str)-retraction to be evaluated for 225 speakers. Center of gravity measurements for /s/ in (str) were normalized to each speaker’s sibilant space. The results show a clear trend toward retraction of (str) in apparent time, something that no study of American English (str)-retraction has demonstrated so far. Many of the speakers in the data show evidence of phonological reanalysis of /s/ in (str) as /sh/. Lastly, evidence is given that sheds light on the plausibility of competing theories of the origins of (str)-retraction, and some connections are made that allow us to make a first approach toward understanding this variable’s social evaluation in Philadelphia.