Jackson is the southern end of the longest railroad platform in America under State Street. This island platform for the two track line stretches from this station to the Lake Station passing through Monroe and the abandoned Washington Street Station and the now boarded up start of construction for the Block 37 Super Station). The station's single platform has been renovated with mosaic tile in the arched ceiling of the platform, with small mosaics and Js for Jackson, illuminated signage with strip maps, arrows pointing towards the station exits, and first generation LED traveler information signs hang from each edge of the arch. In the middle of the platform, two staircases lead downstairs to an underground tunnel to the CTA Blue Line's Jackson Station on the Dearborn Street Subway. The station has an additional underground connection to the Blue Line outside of fare control via a passageway connecting the northern mezzanines, and is the only wheelchair accessible connection. There is also a free Ventra card (formerly farecard) transfer to the Loop's Herold Washington Library State/Van Buren Station along Van Buren Street.
The station has two mezzanines, one at the northern end of the stopping area for trains, and one towards the southern end of the long platform. The southern mezzanine contains turnstiles that lead to a staircase/escalator north on the platforms, followed by a platform elevator down a short mezzanine to the platform, and a combined staircase/escalator that leads to a high exit only turnstile. Exits from this mezzanine are up to each side of State Street between Jackson and Van Buren, with an up escalator (farther north) and staircase to the east side of the street, and the street elevator (farther snorth) and staircaes to the west side of the street.
The northern mezzanine has a similar layout except no elevator, a combined escalator/staircase from the northern end of the platform leads up to a bank of turnstiles. A staircase leads up to High Exit only turnstiles beyond the northern stopping point of trains. This mezzanine contains an underground (out of fare control) passageway to the Blue line's Jackson Station on the Dearborn Subway, and an exit only, always up escalator and staircase up to each side of State Street between Jackson and Adams. The direction of these are in reverse, on the east side of the street the escalator is the northern exit, south side of the street the southern one.