Final answer:
The Supreme Court's 1896 Plessy v. Ferguson decision is a historical event that supports Degler's interpretation of the rise of Jim Crow segregation by legally sanctioning 'separate but equal' and reinforcing the custom of racial separation into law.
Step-by-step explanation:
One specific historical event that can be used to support Degler’s interpretation of the rise of Jim Crow segregation is the Supreme Court's decision in the Plessy v. Ferguson case of 1896. This landmark case upheld the constitutionality of racial segregation under the “separate but equal” doctrine. It served as a justification for furthering segregationist policies, which were codified into law in the Southern United States and became more entrenched in the decades following the Civil War.
The ruling essentially gave legal sanction to states to separate the races in nearly all aspects of public life, including transportation, schools, and other public facilities. As a result, states expanded Jim Crow laws leading to a systematic de jure segregation that lasted well into the 20th century. The custom of racial separation thus became hard-law, reinforcing Degler's observation that legal segregation mirrored the societal changes as African Americans were beginning to assert their rights and economic independence.