Fares at this price start as soon as next week. Depart on Tuesday, Wednesday, Saturday, and the occasional Friday travel through December 19, 2018. Next year, seats are available daily, except on Thursdays during the travel window of January 8 through February 13, 2019. Dates in October and November are almost sold out, but there is still some scattered availability. For your best bet on finding this fare try the winter months as they haven't booked up as quickly.
As an example, I found seats departing ORD on Friday, January 18 and returning from DFW on Monday, January 21, 2019. Perfect for a quick weekend getaway from the Chicago chill in January.
This fare also works in reverse, from Dallas to Chicago for the same price. However, the availability isn't quite as good.
One-way flights are available for $41 a piece, so you could purchase one of those and create an itinerary around it if you're flexible.
Since everything is bigger in Texas, you'll be happy with this large selection of Lonestar-sized rooms for the sample dates on Hotelwatchdog.