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We had a large common domain, already added by the several States for the common benefit of all; purchase and war might make large additions to this common domain; hence the power over existing and future territories, with the stipulation to admit new States, was conferred.

Robert Augustus Toombs (1860). “Speech of Hon. Robert Toombs: On the Crisis. Delivered Before the Georgia Legislature, December 7, 1860”, p.4
We had a large common domain, already added by the several States for the common benefit of all; purchase and war might make large additions to this common domain; hence the power over existing and future territories,