Historical Map: New York City Transit System Morning Peak Flow, 1954
A beautiful old map showing scheduled morning peak service (both actual service and absolute maximum capacity) into Manhattan below 60th Street. The thicker the lines, the greater the service — much like modern service frequency maps! Being 1954, the subway is still divided into its three separately run divisions: BMT (Yellow), IRT (Blue) and IND (Red).
(Source: Ward Maps’ Facebook Page — lots of amazing old maps here!)