The OEM giant purchased the Peoria professional office building on the corner of the block, adjacent to its corporate headquarters, the Journal Star reported.
It means Caterpillar owns the entire Adams Street block between Main and Fulton streets downtown.
The purchase follows the acquisition of another building on the street for $1.5 million in December.
"The company's purchase of the Peoria professional building is a strategic transaction,” Caterpillar said in a statement released to WYZZ TV.
“Ownership of this property allows us greater flexibility in having ample and available workspace to accommodate our employees as needed in the future.”
Caterpillar previously announced plans for a study into a new headquarters in downtown Peoria.
Whether the company will construct an entirely new building or simply redevelop the existing HQ remains unclear.
The results from the study are expected to be released sometime this year.
