The Louisiana Purchase happened in 1803, when the treaty was signed on April 30, 1803, in Paris.

Quick Scoop: Key Dates

  • Treaty signed: April 30, 1803.
  • Senate ratified the treaty: October 20, 1803.
  • Public announcement in the U.S.: July 4, 1803.

So if you’re just answering a quiz that asks “when did the Louisiana Purchase happen,” the expected date is 1803 , often specified as April 30, 1803.

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