I got asked a question related to the last post on the 1979 fire: Doesn't the Z-shaped mill on Market Street have a name? Without digging any deeper, I said not to my knowledge. But, I wrote a lot more than that about the history of the millyard, so I'll dump it here ;-)
You are correct that Market Mills is at least not the original name.
The original complex that today is Market Mills and Canal Place was built in the late 1820s as the Lowell Manufacturing Company. On the side facing Dutton St, the long straight mill along the side of the National Park Visitor's Center still has that name on it. Fun fact: There is a canal underneath that parking lot right against that building that runs through the hydro power plant that is attached to CPI and forms the alley with CPIII. There is definitely still water running through it as the foundation started leaking a few months ago, and the canal ended up flowing through the alley. I'm not sure if it turns and discharges into the small wasteway on the opposite side of CPIII, or continues straight under CPII. You can see the entrance to the canal off of the Merrimack Canal if you stand by the railing seperating the parking lot from the water.
Market Street was known as Lowell Street early on - the building on the opposite side of the garage, which many Lowellians know as the old police station and is today the NMTW Credit Union building, was built as a market...I can only guess that caused the street to be renamed. Whether the Lowell Mfg Company being on Lowell street was a coincidence or not, I'm not sure. They must've been built around the same time, and the Suffolk Mills (Wannalancit) used to be on Suffolk St, Prescott Mills on Prescott St, etc.
The Lowell Manufacturing Company tended to name buildings either numbers or what they were for...or at least that's what the ward maps say. It certainly is true simple numbers worked for the early Waltham/Lowell system mills. Today, the original pattern of the mills is best visible (and maybe only visible at this point...) at the Massachusetts Mills and Boott Mills, where the original gable-roofed mills all in a line were later connected with stair towers, and the gabled top floor was replaced with a flat one, or a few more stories, later on. Old maps show Canal Place I as being the "Worsted Mill" for example...because they must've made Worsted fabrics there. Interestingly, the Lowell Mfg Co. was the only one of the ten major mill corporations who made carpets, and in the nineteen-teens, they were the first of the majors to fold, getting bought up by the Bigelow Carpet Company.
Before that could happen however, the Lowell Mfg Co. began a large rebuilding project, starting with the building along the side of the parking lot around 1890, the Z-shaped building the fire was in closer to 1900, then the Canal Place buildings in the years after that (which are all nicely marked with dates) until 1912 or so...right before the sale to Bigelow. Interestingly, I think one of the oldest structures remaining in the yard is one you'd rarely think of as a unique building: The mail room/lobby for Canal Place I survived the rebuild.
Bigelow could not have lasted very long, as the Z-shaped building was the Lowell Silk Mills by the 1920s, or so says the former door right on Market Street where the TV station is today.
By that point, the mid 1920s, quite a few of the major mill companies were in trouble and the formerly unified mill yards were sold off to smaller interests, a process that accelerated during the Depression and never stopped.
In other words, much shorter ones, that I already stated at the beginning, I don't think Market Mills was used before the apartment conversion, but I don't know. I do know it certainly wasn't the original name. :-P