Final answer:
The statement that the March on Washington began a period of uninterrupted unity within the civil rights movement is not true; while major in its impact, it did not lead to unchallenged unity thereafter.
Step-by-step explanation:
The statement about the March on Washington of 1963 that is NOT true is that 'It began a period of uninterrupted unity within the civil rights movement.' While the march was a significant event that succeeded in transforming civil rights into a national cause, with about 250,000 people who gathered in a biracial crowd at the Lincoln Memorial to hear Martin Luther King Jr.'s famous speech which was nationally televised, it did not result in uninterrupted unity. There were still many challenges ahead, and the unity that was showcased during the march faced obstacles in the times that followed.