History of MARC

Can someone provide me with a brief history of MARC and its various services from 1970's until the formation of the agency with its GP40WH's and K-cars? Wikipedia is lacking on the subject and my interest was piqued by seeing a large number of B&W photos from the 1970's taken along the NEC in Maryland. These showed a number of MP54's on local services and I was wondering when those (and the B&O RDCs) were replaced by an MDDoT branded service and finally when MDDot was replaced by MARC. Did the B&O operate any locomotive hauled commuter trains in the 1970's? Where did MDDoT get all of its pre-GP40 Push-Pull equipment and heritage coaches? What replaced the MP54s and what were services on the Penn Line in the PC and early MDDoT days? Finally when did the Orangeville Engine Terminal close and what replaced it?

Thanks.

Most, if not all, of the heritage coaches came from NJT when they retired them circa-1990. I have scores of Railpaces from the '80 and early '90s, and most of them show at least one odd consist running on MARC, especially on the B&O side.