The answer is:
August 28, 1963, during the March on Washington for Jobs and Freedom in USA
Explanation:
"I Have a Dream" was a speech delivered by American civil rights activist Martin Luther King Jr. on August 28, 1963, during the March on Washington for Jobs and Freedom. In this speech he calls for an end to racism in the United States and demanded for civil and economic rights for black people in USA. This speech was heard by at least 250,000 civil rights supporters.
