Covina, CA was incorporated in 1901 and West Covina, CA was incorporated in 1923. By 1950 West Covina was bigger than Covina, and today it is over twice as large (106K vs. 51K).
On the Palos Verdes Peninsula, the city of Palos Verdes Estates was the first to be developed/incorporated (1939), but is only about 13K people; Rancho Palos Verdes was the most recent to be incorporated (1973) but is the largest at 41K; Rolling Hills Estates (incorporated 1957) is only about 8K people, but is far and away the commercial center for the area; the simplest-named Rolling Hills (incorporated 1957) is the smallest (less than 2K) and is residential-only. FWIW people usually just refer to the whole area as "Palos Verdes" (or more locally, "the hill").
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If accepting the concept of San Francisco/San Jose (i.e., the historically dominant city of a metro being passed in population) you may also consider these geographically closer pairs:
-Riverside being larger than San Bernardino (although they're probably equal now in terms of commercial importance)
-Anaheim being larger than Santa Ana (again, they're probably equal from a business standpoint; Santa Ana is the governmental center, while Anaheim is the tourism center)