Greenwich (AKA "The Wich") is a small town located in Huron County. There are only around 1,600 residents, but the rail activity is amazing. Its location is approximately 10 miles east of Willard, Ohio and CSX's Willard Yard and about 50 miles east of Fostoria.
CSX controls the old New York Central route from Cleveland to Indianapolis and St. Louis. At Greenwich, this mainline crosses the old B&O Akron Division. The old NYC line unites with the Willard Subdivision of CSX at Greenwich, passes through Willard Yard and pass through Fostoria ultimately to Chicago.
In addition to CSX trains, a couple of W&LE trains go through Greenwich each day.
Greenwich is located on Rt 224 between Willard and New London (another nice place to watch trains). As you drive into Greenwich (watch your speed!), turn north at the BP station on the east end of town on Kniffin Street. Drive about 1/4 and cross over the first set of CSX tracks (these go from New Castle, PA through Fostoria, to Chicago) and park on the right. Do not park between the diamonds as that is railroad property. The CSX policeman for this area is a very nice man, but he will tell you not to park on railroad property.
I have found that Greenwich is very active early in the morning (i.e., 3 am until around 9:00 am) and then again in the late afternoon or early evening.