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The correct spelling of this street name is BANNAN PL, per the official dedication map (between UNION ST and GREEN ST, and STOCKTON ST and GRANT AVE). Unfortunately, this issue is not uncommon, and is exacerbated by the sign in place, and by the information that is returned by popular search engines, for example here, here, and here.
SF residents fight City Hall to get nameless street on maps
This is an interesting article, with photographs, that was published on 04 May 2019 about JOHN'S WAY. Note the use of an apostrophe in light of the information above.