UPDATE: Recently visited area north of Bloomington, Indiana.
See: https://digitalrockhound.com/2019/06/geode-hunting-near-bloomington-indiana.html

Map showing counties where geodes can be found in Indiana.

Geodes can be found from in the southern third of the state. Popular counties to find geodes include Brown, Monroe, Morgan, Lawrence and Washington.
and scattered on the ground.

(Map Generated by DRC 3.0)

Read more :

Geodes
Bedford, Indiana
Geodes containing barite, calcite, dolomite, marcasite, millerite, pyrite, quartz, & sphalerite occur in a layer of limestone exposed by the road-cut along State Route 37, approximately 10.5 miles north of Bedford (just south of the Monroe Lake exit).

In south-central Indiana geodes can
be found in the walls of road cuts
and other exposures of rocks of the
Harrodsburg Limestone and Ramp
Creek Formation. For several miles
on either side of this outcrop area,
geodes are abundant along streams