Okla. Stat. tit. 66, § 66-14: What property subject to mortgage

All rolling stock of any railroad corporation organized under

the provisions of this article, used and employed in connection with

its railroad, and all fuel necessary to the operation of the same,

are declared and shall be held to be fixtures; and all such

property, and all additional rights-of-way, depot grounds, and other

real property, acquired subsequently to the execution of any trust

deed or mortgage which shall have been described or provided for

therein, shall be subject to the lien thereof to the same extent as

the property therein described, which the corporation owned at the

time of its execution.