There are hereby authorized to be appropriated such sums as may be necessary to carry out the purposes of this subchapter, but not more than $4,500,000 shall be appropriated for the acquisition of lands or interest in lands.

(Pub. L. 90–544, title V, § 506, Oct. 2, 1968, 82 Stat. 930; Pub. L. 94–578, title I, § 101(9), Oct. 21, 1976, 90 Stat. 2732.)