Explain the reason for the Lahore Session of the Congress in 1929

Explain the reason for the Lahore Session of the Congress in 1929 to be called the historical session.

Indians demonstrated against the Simon Commission as it had no Indian representative in it. So in an effort to win the support, Viceroy Lord Irwin announced an uncertain offer of‘Dominian status’to India and a Round Table Conference to discuss a future constitution.
The expectations of the Congress were not met by this announcement. So at Lahore session, the Congress President Jawaharlal Nehru passed a resolution of declaring ‘Purna Swaraj’ in December 1929. After declaring ‘Purna Swaraj’ or complete independence, the Congress took active steps to launch the Civil Disobedience Movement.