I have written an article on the history of 'Maggie May', from the persepctive of a Beatles fan and researcher, rather than an expert in traditional song. The research I have done matches alot of what has been written here in this thread. I believe the 1830 dating, as appears on Wikipedia, is incorrect and that it is very much the product of the Music Hall era, a parody of 'Darling Nelly Gray'. It most likely dated to the early 1870's, and was possibly first performed at the The Eastern Music Hall in Limehouse, in the wwek 9-16th October 1870, by the London comic Edgar Wilding in front of an audience of sailors from the West India docks and 'ladies of the night'.

It can be viewed at the adress below:

https://www.docdroid.net/sGHmAgV/maggie-may-the-story-of-a-liverpool-classic.pdf.html