Yep. Louisiana Purchase, Seward’s Folly (Alaska Purchase), the Mexican Cession.
Even though the Constitution specifically said the Federal government was to own no land other than ten square miles for DC and whatever was needed for ports and bases, it clearly purchased all of the west from France, Mexico and Russia when the Constitution was practically shiny-new.
I have no idea how they justified doing that without an Amendment allowing it, but there is no question the purchases were made.
Two of the three can easily be justified by national security considerations. There are powers implicit within the Constitution that allow/assist it to carry out specified powers. At the convention the issue of nailing the document down to specified powers was raised but it was roundly rejected and wisely too.
Hamilton’s interpretation of what is constitutional is the definitive one as laid out in the Essay on the National Bank, one of the most brilliant state papers ever written.
In it he says that something is constitutional if it has not been specifically forbidden, furthers the implementation of a specified power, or does not violate the spirit of the constitution.
Its legality is also implied by the concept of sovereignty.
Alaska was the fulfilment of the Manifest Destiny idea - whereby we should take over as much of the continent as possible. Three or four attempts on Canada had failed.
Btw our greatest jurist, John Marshall, said that when pondering any case before the Court the first thing he did was consult the Federalist, 60+% written by Hamilton.