Definite articles are used before the name of seas, oceans, rivers, deserts, mountain ranges, gulfs, peninsulas, etc. Moreover, article the also precedes constructions such as the city of New York, the University of Oxford, the Republic of Mexico.
Incorrect The 10 campuses of University of California open their doors to all who work hard and dream big.
The proper noun phrase University of California requires a definite article before it.
Correct The 10 campuses of the University of California open their doors to all who work hard and dream big.