I've shown this one before. The northeast corridor should all be on one time, and that is AST. I've divided my map based on metropolitan areas and DMA's. I've renamed MST as Western Standard Time, but for description purposes below, I'll use MST

States that are divided
NY: Rochester and Buffalo EST, rest AST
PA: Philly, Harrisburg, Scranton DMA's, Pike, and Fulton County AST; Pittsburgh, Erie, Altoona DMA's plus Mercer, McKean, and Potter Counties EST
MD: Garrett County EST, rest AST
WV: Washington and Harrisonburg DMA counties AST, rest EST
VA: Washington, Richmond, Charlottesville, Harrisonburg, Norfolk AST; Roanoke, Bristol, and Greensboro DMA area EST
NC: Norfolk DMA counties AST, rest EST
MN: MSP DMA EST, rest CST
IA: Quad Cities DMA EST, rest CST
MO: Hannibal/Quincy, St Louis, Cape Girardeau DMA's EST, rest CST
AR: Memphis and Jackson DMA counties EST, rest CST
LA: New Orleans DMA EST, rest CST
MT: Billings, Glendive, and Bismarck DMA counties CST, rest MST
WY: Salt Lake City DMA counties MST, rest CST
AZ: Apache County CST, rest MST
WA: Spokane DMA MST, rest PST
OR: Boise DMA counties MST, rest PST
CA: Siskiyou County PST, rest MST