Final answer:
The words "San Francisco," "Baltimore," and "Atlanta" are all proper nouns naming cities, and proper nouns are capitalized as they denote specific places.
Step-by-step explanation:
The words "San Francisco," "Baltimore," and "Atlanta" are all proper nouns since they are names of cities. Proper nouns are specific names given to individual people, places, institutions, or events, and they are always capitalized. These city names sometimes contain elements that tie back to historical or linguistic roots, such as the suffix "-ton" in other city names, which means "town."