Complex sentence: The first okapi born in captivity outside Congo was at the Antwerp Zoo, Belgium in 1953; the first born in North America was at the Brookfield Zoo in Illinois in 1959.
Split into simpler sentences: The first okapi born in captivity outside Congo was at the Antwerp Zoo, Belgium in 1953. In North America, the first okapi was born at the Brookfield Zoo in Illinois in 1959.