Tennessee Valley Railroad, Chattanooga TN operates "Summerville Steam Special" every Saturday and some Sundays in October and early November with Southern #4501. Of special note, Double-headers are scheduled to operate on Summerville Steam Specials on October 21, 28, and November 11, 2018. Double-headers at TVRM not only feature two steam locomotives (#630 and #4501) but both locomotives were built new for the Southern Railroad, which served Chattanooga, Tennessee.
Reading Blue Mountain & Northern Railroad, Reading, Pennsylvania operates Fall Foliage Excursions featuring locomotive #425. This locomotive, in a unique dark blue paint scheme, is a railfan favorite for good reason.
Steam Railroading Institute, in Michigan operates Pere Marquette #1225 for a special "Curwood Highlander" Excursion from Alma to Owosso, Michigan on October 20, 2018.
And plenty more! Be sure to check out "Steam by State" and plan a train ride in the Fall.