You'll see some pretty big figures for the NY families at their peak, ranging anywhere from around 200 to 400+. In my opinion, the estimates before the 1980s are not as reliable and become more suspect the further you go back. The max memberships D'Arco listed in his book were smaller. 300 for the Genovese and Gambinos, 150 for the Colombos, and 125-140 for the Luccheses and Bonannos.

From what I have read, New England and Philadelphia were around 70. New Jersey 60. Pittsburgh 30-35. Cleveland 50-60. Milwaukee 60 (not sure how much I believe that one). Detroit 75-100 (not sure how much I believe that one either). St Louis 35-40. Tampa 25-30. New Orleans 20. San Jose 30-35. San Francisco 25. Los Angeles I've seen as high as 60-70 in the 1950s but I find that hard to believe. Chicago has always been hard to read for obvious reasons but I've seen a max of 150-200, supposedly peaking in the 1970s. Not sure about Denver but, considering it was more of a gambling syndicate built around the Smaldones, the actual membership would probably be as small or smaller than anything listed above. Same for Dallas.

What's interesting is, if you add up all the possible max memberships of all the families it is closer to half of the 5,000 member so often quoted for peak Mafia membership.