Whatever one writes about Chinatown is surely too little.  Historically, this area is known by xenophobic outsiders like the 19th century labor organizer Dennis Kearney (whose name is spelled differently from Kearny Street) for intrigue... although the intrigue was usually plotted against hard working Chinese rather than by Chinese.  An example of this shows up in a literary fragment on the Nob Hill page. 

For its residents, Chinatown is the sweetest of homes, maybe more so in the imperfectly remembered youth of old age, a ghetto in ways more positive than negative where the smells of dinner and the jostling of crowds are constant features of life.  Catch a MUNI No. 30 Stockton bus anywhere south of Washington Square to get an idea of the jostling. 

Chinatown is Grant Avenue from Bush Street to about Pacific Avenue, and the neighboring portions of Kearny Street on the east and Stockton Street to the west, north of the tunnel, and the area around Portsmouth Square at Kearny and Washington Streets.  Old Saint Mary's Cathedral is in Chinatown (at Kearny and Pine), reflecting that the neighborhood has grown beyond its historic boundaries. 

The  Americans Plant a Flag

Grant Avenue at dusk

Grant Avenue on a different day.  The vertical sign on the right next to a building with fire escapes has the Chinese characters "ji`u jin shan" (the first character is difficult to see), which means "San Francisco".   I can't translate the bottom two characters.

Portsmouth Square, where the U.S. flag first flew in Yerba Buena settlement, as described at left.  This was also SF's main plaza in the early years.  (Northwest corner, Lum Place and Washington Street)  

An American naval officer sat in the U.S. ship Portsmouth, anchored off a small hamlet in San Francisco Bay, scratching out a letter in bad English to a compatriot on shore.  The epistle, which was addressed to William A. Leidesdorff, the American Vice-Consul in this nominally Mexican town, was not friendly.  It warned that by the end of the morrow, July 9, 1846, the village would not even be nominally Mexican.

At 1/2 past seven oclock to morrow morning I propose landing a considerable body of men under arms.  And to march them from the boats to the flag staff in Yerba Buena, upon which at 8 oclock, I shall hoist the Flag of the U States under a salute of twenty one guns from the Portsmouth. afterwhich, [sic] the Proclamation of the Commander in Cheif [sic] Commodore Sloat will be read in both languages for the enformation [sic] of all classes.

The events of the next day amply fulfilled Captain John Montgomery's threat.  He landed his troops as planned, hosited the flag, read the proclamation, and took over in the name of "U States." 

The sailors and marines had "conquered" the site of what was to become one of the world's most important and fascinating cities.

From San Francisco 1846-1856: From Hamlet to City by Roger W. Lotchin.  Lincoln: Univ. of Nebraska Press, 1979.  ISBN 0-8032-7904-3