The 1912 Central Union Telephone Co. directory included this handy list of fire alarm locations. The directory also prominently asked residents not to call the phone company to find out the location of a fire, as that “seriously interferes with the regular business of the exchange.”
Note: This entry has been updated to include the full list of alarm boxes. 
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Where was Chestnut? That’s the only street I don’t recognize.
Liz: Good catch. Chestnut was either 16th or 17th Street at Moffatt — probably 16th. It’s hard to tell because streets on that area of the east side jog between about Clear Lake and Carpenter. Newspaper records are incomplete, and the only online map I have from around then is reproduced too small to read street names. Just to complicate things further, it looks like numbered streets replaced named ones on north-south streets somewhere in the decade of the 1910s, but some people kept using the old names for a while afterwards.
P.S.: This list is incomplete. I need to add south-side alarm boxes as soon as I can find the memory chip that has that photo on it.