Nearly 3,000 people attended the annual stair-climbing event. Participants climbed 103 floors — about 2,100 steps in all — to the Willis Tower's SkyDeck level.
Organizers said the event raises about $1 million each year to support rehabilitation care and research at the institute.
Kirk's office declined to comment on his participation in the event or when he might return to Washington. But Joanne Smith, the Rehabilitation Institute's CEO, said his ability to finish "demonstrates that Sen. Kirk is back and perhaps better than ever."
U.S. Rep. Jesse Jackson, another prominent Illinois leader receiving medical treatment, hasn't made a public appearance since June. The Chicago Democrat, who is seeking re-election Tuesday, is expected to remain at Minnesota's Mayo Clinic through Election Day. His office has not indicated when he'll return to work.