I can probably answer some of firepost's questions. Sometime in the 70's (I think) SFD had staffing cut. They decided to have what they called ERS (Expanded Response System) engines throughout the city to try and make up for lost manpower on fire scenes. I think these were all known as "Attack" units. They were staffed with 6, while all of the other engines in the city were staffed with 3. At least one of the first three engines on a first alarm would be an ERS engine. Ladders were all staffed with 5. Eventually the system evolved to having the ERS engines staffed with 5. When I moved here in '89, the ERS engines were 2, 9, 10, 13, 25, and 36. There may be more that I'm forgetting or didn't know about. They were all staffed with 5 and all of the other engines were staffed with 3. Typically you'd have the first 2 engines at a fire staffed with 3, then the third engine coming from a long way away staffed with 5. As you might imagine this didn't make a whole lot of sense.
Then in the '90's the city made a concerted effort to get staffing up to 4 on all companies. They dropped staffing on the ladders to 4 and began gradually increasing staffing on all of the engines to 4. For awhile, there were some engines that were still staffed with 3. These were known as "attack" companies to differentiate them from engines staffed with 4. Eventually sometime around 2000 every fire company in the city was staffed with 4, as they continue to be today.
Hope this helps!
Then in the '90's the city made a concerted effort to get staffing up to 4 on all companies. They dropped staffing on the ladders to 4 and began gradually increasing staffing on all of the engines to 4. For awhile, there were some engines that were still staffed with 3. These were known as "attack" companies to differentiate them from engines staffed with 4. Eventually sometime around 2000 every fire company in the city was staffed with 4, as they continue to be today.
Hope this helps!