Looking for recommendations on where to go for road trip from Chicago with a 1.5 yr old. Do not want to drive more than 8-9 hrs.
We do not want to go anywhere in WI or MI.
Some thoughts were Pittsburgh , Niagara falls in NY,

Later this month DW and I are taking the Lake Shore Limited out of Chicago (leaves 9:30PM CT). and arrives in Erie PA a little after 7AM ET. We'll have some breakfast before the Enterprise opens at 9.
Niagara Falls is within your time frame from Erie but not from Chicago.
Be sure to know the passport requirements for you and the 1.5 year old if you want to go Niagara Falls Ontario. The view is better from the Canadian side.

Could you provide a information on what you and your family would enjoy doing/seeing?

We live in the Chicago suburbs and have kids. Some road trips we have enjoyed:
-Mammoth Cave Kentucky - we rented a house on a little lake. The water was so warm and was great for kids. We did Mammoth Cave, and some of the kitschy sites nearby. We liked Kentucky Down Under. (Nashville is not far and you could add that to the trip).
-Indianapolis - Only 3 hours. Has a great Childrens Museum and we LOVE the State Fair in August. We also stop in Turkey Run State Park on the way there or home to go hiking and canoeing.
St. Louis - Less than 5 hours. There is a lot to do there! Great Children's Museum. The City Museum is crazy and amazing but better for kids a little older than yours. An AWESOME free zoo, great bbq, the Arch. A science museum that is free. Grants Farm.
Springfield, IL is 2.5 hours and has a lot to see and do too. The Lincoln Museum, the Capitol, Lincolns Home. Lincolns New Salem. The Old State Capitol. Lincolns Tomb. An outdoor theater in summer.
Smoky Mountain National Park is around 9 hours away. Lots of cabin rentals in the area. Ours had a nice pool in the cabin complex.
Niagara Falls is about 9 hours away. We did it as the start of our long East Coast Road Trip.

Any of the Tennessee state parks. Montgomery Bell is near enough to Nashville, so you can do city things (well, country city things) and historic things (Andrew Jackson home, The Hermitage).

But I wouldn't easte any time booking.

Take a look into reserving a week at the Galena Chalet. You would never believe that you are actually in Illinois - it looks like you are sitting in a magnificent chalet overlooking Lake Lucern in Switzerland. It's spectacular. It's an easy drive to Galena (about 2.5 hours from Chicago) and the house is baby friendly because the owners have a 1 yr old. The weekend rates are very high because it is so highly demanded during the weekends but if you take one of their 5-day reduced week blocks you can stay an entire 5 days for the same price as a 2-night weekend stay. I think they are about $2000 for 5 nights (Sun-Thurs). Usually they rent weekends for $1000-$1200/night. It's very high-end and - they have a beautiful garden out front with a working fountain and the interior is brilliantly designed. It is a cool place to go to any time of the year and it's nice that it's so close to Chicago. Their website is www.GalenaChalet.com