Historical source: National Archives, Constitution of the United States: A Transcription. Original wording is distinguished from explanatory notes below.
Article I establishes the legislative branch of the federal government: the House of Representatives and the Senate. It explains how Congress is organized, how laws are made, which powers Congress may exercise, and which limits apply to Congress and the states.
Original text — Section 1
All legislative Powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives.
Read the complete original Article I
Article I contains ten sections. For the full original wording of all ten sections, including the original spelling and punctuation, read the National Archives’ official Constitution transcription.
Amendments and historical provisions
Some provisions of Article I were later changed or superseded. The Fourteenth Amendment replaced the original three-fifths apportionment formula; the Seventeenth Amendment established popular election of U.S. senators; the Twentieth Amendment changed when Congress meets; and the Sixteenth Amendment clarified congressional authority to tax incomes. The original wording is preserved as history, not presented as the current rule where an amendment has changed it.
Primary source: Read the Constitution at the National Archives.