From an Amtrak press release:
In further anticipation of its busiest travel season, Amtrak is adding another round-trip to and from Holland, Mich., on the Sunday after Thanksgiving.
The holiday is the busiest travel week of the year, and to accommodate the expected surge of riders, Amtrak will operate every available passenger rail car in its fleet and is scheduling extra trains and adding capacity on other routes.
The attached schedule provides information on these extra trains that will operate in addition to the Amtrak Pere Marquette trains sponsored by the Michigan Department of Transportation, with slight changes in schedules to Trains 370 & 371 to accommodate the additional round-trip, Trains 372 & 373.
Amtrak carried a record 737,537 passengers during the 2012 Thanksgiving travel period, up 1.9 percent over the previous year and the prior record set in 2011.