The incident occurred around 2:22 a.m. at Ida B. Wells Drive and Clark Street.
Police said an on-duty officer was directing traffic when a Dodge Charger failed to stop and struck the officer.
The driver and a passenger in the Dodge were both taken into custody.
The officer was taken to Northwestern Memorial Hospital with non-life-threatening injuries.
Police said the incident appears to be alcohol-related and two handguns were recovered from the vehicle.
Meanwhile, downtown was flooded with traffic overnight with people in their vehicles celebrating Mexican Independence Day.
Fireworks lit up the sky as people celebrated through the night. Police blocked off several streets as people made their way around town, honking horns and waving Mexican flags.