75 ILCS 5/5-4
The library board shall determine when it will proceed with the construction of a building, or with the purchase of a site or building, or with the remodeling, repairing, or improving of an existing library building, or the building of an addition thereto, or with the purchase of necessary equipment, or the acquisition of library materials such as books, periodicals, recordings and electronic data storage and retrieval facilities in connection with either the purchase or construction of a new library building or the expansion of an existing library building, or any or all of these things. The board may proceed at once or may determine to wait and allow the fund to accumulate. If the board determines to let the fund accumulate, it shall invest the money in good interest paying securities, such as are authorized by law for the investment of trust funds, there to remain until the same is needed for any or all of the purposes enumerated aforesaid. The board may contract to accomplish any or all of the purposes enumerated aforesaid, and may apply the proceeds of the tax as collected, toward payment therefor.
75 ILCS 5/5-4