Complex sentence: Adam Clayton Powell, Sr. identified as black in the South and in his life, but later in life easily passed as white for convenience when traveling by train in the South; he used it to gain better accommodations in the segregated railroad cars.
Split into simpler sentences: Adam Clayton Powell, Sr. identified as black in the South and in his life. Later in life he easily passed as white for convenience when traveling by train in the South; he used it to gain better accommodations in the segregated railroad cars.