Gandhi's famous March to Dandi in 1930 was an act to protest against Great Britain's tax on what?

The Salt March, also known as the Dandi March and the Dandi Satyagraha, was an act of nonviolent civil disobedience in colonial India initiated by Mohandas Karamchand Gandhi to produce salt from the seawater in the coastal village of Dandi, as was the practice of the local populace until British officials introduced taxation on salt production, deemed their sea-salt reclamation activities illegal, and then repeatedly used force to stop it. The 24-day march began from 12 March 1930 and continued till 6 April 1930 as a direct action campaign of tax resistance and nonviolent protest against the British salt monopoly, and it gained worldwide attention which gave impetus to the Indian independence movement and started the nationwide Civil Disobedience Movement.

Salt Satyagraha succeeded in drawing the attention of the world. Millions saw the newsreels showing the march. Time magazine declared Gandhi its 1930 Man of the Year, comparing Gandhi's march to the sea "to defy Britain's salt tax as some New Englanders once defied a British tea tax. Civil disobedience continued until early 1931, when Gandhi was finally released from prison.

More than thirty years later, Satyagraha and the March to Dandi exercised a strong influence on American civil rights activist Martin Luther King, Jr., and his fight for civil rights for African-Americans in the 1960's.