The American Eagle (North) Terminal was built sometime in the 1990s to handle the expansion of American Eagle's regional flights as well as for the arrival of regional jets. The small terminal had not only covered walkways/small jetways but also remote parking that passengers were bused to (usually used in those days by Saab SF340s and the ATRs when they were common in DFW).
Air Ports, Transportation - Aviation
Following capacity cutbacks at American following 9/11, the North Terminal (which was accessed by a bus leaving Terminal A) was closed and Eagle flights were moved to Terminal B.
The terminal as of May 2007 still remains closed.