Indiana Code Title 36. Local Government § 36-4-1-1

Sec. 1. (a) Municipalities are classified according to their status and population as follows:

(b) Except as provided in subsection (c), a city that attains a population of thirty-four thousand (34,000) remains a second class city even though its population decreases to less than thirty-four thousand (34,000) at the next federal decennial census.

(c) The legislative body of a city to which subsection (b) applies may, by ordinance, adopt third class city status.