PLVI stands for Peak Land Value Intersection--that is, where, in the city, the rents are costliest. It is, for all intents and purposes, the "center" of the city.
And, like the magnetic North Pole, it drifts. It can drift obliquely slightly, but this drift tends to favor the direction of the favored quarter. If the favored quarter is the west, it drifts in a westerly direction; if it's southeast, southeasterly. Sometimes accidents of geography can really nail it down, but it seems to head a couple of blocks further every generation or two.
Because High--later Market--Street was cluttered with market sheds for most of Philadelphia's early history, the PLVI, "directed" as it is by the elite in their favoritism patterns, favored Chestnut. At the time of the Revolution, the best evidence suggests it was at 2nd and Chestnut. Philadelphia's early financial district grew up along the 400 block of Chestnut, placing the PLVI there. By the fin-de-siècle, the largest department stores clustered around 8th and Market (Strawbridge & Clothier, Gimbel Brothers, and Lit Brothers), making that the PLVI, and by the 1920s it had jumped west to the corner of Broad and South Penn Square (City Hall), and thence migrated south to Broad and Chestnut, which is where Jane Jacobs found it (in her critique of it being the home of banks and not much else). It moved to 15th and Market not long after her writing, and then to 17th and JFK by the 1980s, when the postmodern skyscrapers were built--most recently the Comcast Center.
Bacon predicted it would move to 30th Street Station, which it is doing (slowly). The PLVI sat around City Hall for the first half of the 20th century in part because it was the point of maximal transportation access: the Reading Terminal and the Pennsylvania's Broad Street Station, to varying degrees of literalness, abutted the building. When Suburban replaced Broad as the Pennsy's main commuter station, and 30th Street its main intercity station, this all but guaranteed a long term westward movement of the PLVI. Something similar happened in New York, where Midtown Manhattan developed between Grand Central and Penn Station.
So what kinds of examples can you find in your city of PLVI drift? Former PLVIs are etched into the architecture. Where was the financial district located when your city was founded? A hundred years later? Two? Philadelphia, being one of the oldest major cities in the U.S., has more history to draw on than most--but that does not necessarily mean its PLVI drifted the furtherest.