35 ILCS 605/22
The lands selected under the act of congress entitled "An Act granting the right of way, and making a grant of land to the states of Illinois, Mississippi and Alabama, in aid of the construction of a railroad from Chicago to Mobile", passed September 20, 1850, and authorized by this Act to be conveyed shall be exempt from all taxation under the laws of this state, until sold and conveyed by the Illinois Central Railroad Company or the trustees designated in this Act. The stock, property and assets belonging to the company shall be listed by the president, secretary or other officer, with the Department of Revenue, and an annual tax for state purposes shall be assessed, upon all the property and assets of every name, kind and description belonging to that company. Whenever the taxes levied for state purposes shall exceed 3/4 of 1% per year, such excess shall be deducted from the gross proceeds or income required to be paid by the company to the state, and the company is hereby exempted from all taxation of every kind, except as herein provided for. The revenue arising from such taxation, and the 5% of gross or total proceeds, receipts or income aforesaid, shall be paid to the Department of Revenue and covered into the general revenue fund in the state treasury and applied to the payment of interest-paying state indebtedness until the extinction thereof. In case the 5% provided to be paid into the state treasury and the state taxes to be paid by the corporation do not amount to 7% of the gross or total proceeds, receipts or income, however, then the company shall pay the difference, so as to make the whole amount paid equal, at least, to 7% of the gross receipts of the company.
35 ILCS 605/22