"We had two top priorities as we looked to move our headquarters operations," Easter Seals COO Don Jackson says. "First, we wanted to assure that we were fully accessible for our staff and the people with disabilities we serve and, second, we were looking to do business in an environmentally friendly manner. It was the right thing to do."

The firm achieved the LEED Silver rating for efforts including recycling during construction; designing the space to utilize natural light; and reusing doors, ceiling tiles, lighting, hardware, and furniture and furnishings from the old office. In developing its new space, Easter Seals worked with the SmithGroup on architecture and design, Environmental Design Services' engineers and general contractor Clune Construction Co.

The building is around 85% occupied, with asking lease rates that range from $15 to $21 per square foot net. Built in 1973, the 110-story property is owned by 233 S. Wacker LLC, which includes American Landmark Properties, the Chetrit Group and the Moinian Group. Formerly known as the Sears Tower, the tallest building in the Western Hemisphere was recently renamed to Willis Tower, for the insurance company which took occupancy of 140,000 square feet there over the summer.