Despite this being one of the most detailed 20th century maps on this website, it’s a little fuzzy and might not be as useful for mapping your family’s history as you’d hope!
Wards and Boroughs
Clearly the main point of the map was not the individual streets but the boundaries around them, marked here in red, with red labels.
The thicker red lines mark out the boroughs, which were represented in Parliament by an MP. The thinner red lines are wards, which had representatives on the town council. The wards were also used as organisational divisions, so may be helpful for you locating your ancestors or their businesses on the map from paper records.
(These are my own interpretations of information I can find about the two boundary types. If you can give a more accurate description, please post it in the comments!)
Despite the lack of clarity, this Boundary Commission map can still be used to find old streets. The names are just about readable, and some of the interesting features, such as the density of roads in the centre of town compared to the inner suburbs, is something worth exploring here.
Either way, this is an interesting document of Liverpool’s political position, and should be of help for the amateur historian looking to put a bit of flesh on the bones of lives in the early 20th century.