In April, the City Council voted — 47 to 2 — in favor of the Bloomberg administration’s plan to rezone Harlem’s 125th Street (and some surrounding streets) between Second Avenue and Broadway to make way for the high-rise development of nearly 4,000 apartments.

Many Harlemites feel uneasy about the rezoning. Since half of the housing will be market-rate, some area residents fear that the gentrification already occurring will intensify, and that longtime residents of the community will be forced out. (The other half of the housing will be “affordable housing.”)

Yet is that how it really works? Adding to Harlem’s housing stock might bring down the upward price pressure on the older brownstones and apartment buildings. At least that’s what Economics 101 suggests. In other words, when you have a severe housing shortage, the solution is to build more housing. Yet the fear is that the presence of shiny new housing on 125th Street will cause overall Harlem rents to rise.

Even without the rezoning, 125th Street has changed dramatically in recent years. We’ve seen the move of large national and international chains — Starbucks, Rite Aid, Body Shop, H&M — to 125th Street. One widespread presumption holds that until recently — until the crime reductions of the Giuliani years and after — such chains were simply afraid to operate in Harlem. Whatever the reason, Harlem long endured a desperate lack of retail, as evidenced by the fact that several of the chains report their per-square-foot sales in Harlem to be among the highest of any of their stores.

Now may be a good time to take a stroll along 125th Street.

At Park Avenue, the railroad viaduct and Metro-North station house date from the 1890s. The New York & Harlem Railroad opened its 125th Street station in the 1840s, when this was a country village, decades away from being engulfed by the urban sprawl of northward-growing Manhattan. By the time of the current station, the area was in the midst of intensive development — of, indeed, vast speculative overbuilding, which ultimately led to the many empty new homes being marketed to African-Americans.

As you walk west, at Fifth Avenue look left to Marcus Garvey (formerly Mount Morris) Park, one block away, with its marvelous wooden fire watchtower from the 1850s. Between Fifth and Lenox avenues at 55 W. 125th St. stands the 14-story office building, erected in 1974, where President Clinton maintains his office. At Lenox, note that a block to your right is Sylvia’s (328 Lenox Ave.), the well-known soul-food restaurant, in business since 1962.

At the southwest corner of 125th Street and Adam Clayton Powell Jr. Boulevard (Seventh Avenue) stands the 13-story Hotel Theresa, opened in 1913 and for 60 years Harlem’s tallest building. The “Waldorf-Astoria of Harlem,” the Theresa hosted countless black celebrities during years when they appeared at Harlem venues. Guests included Louis Armstrong, Duke Ellington, Josephine Baker, and Jimi Hendrix.

Fidel Castro stayed there in 1960; the Theresa is where he entertained Nikita Khrushchev. Malcolm X made the hotel the headquarters of his Organization of Afro-American Unity. In the 1950s, Secretary of Commerce Ron Brown grew up in the Theresa, where his father was the manager. Congressman Charles Rangel once worked there as a desk clerk. The hotel closed in 1966, a victim of Harlem’s downward economic spiral.

In 1971, the building reopened as offices. The handsome design, with white-brick façades of rippling oriels, we credit to George and Edward Blum, among the premier New York apartment house architects of their time. Across the street, the New York State Office Building overtook the Theresa as Harlem’s tallest in 1973. Designed by Ifill, Johnson & Hanchard, the state building definitely has its critics, but the boldly framed concrete structure with big glassy bays has a kind of period élan.

On the north side between Adam Clayton Powell Jr. Boulevard and Frederick Douglass Boulevard (Eighth Avenue) stands the Apollo Theater, opened in 1913 as a burlesque house called Hurtig & Seamon’s. The theater did not welcome black audiences until 1934, by which time the name had been changed to Apollo.

It was around then that the Apollo legend began to grow. Amateur night and other events provided early showcases for such performers as Ella Fitzgerald, Billie Holiday, James Brown, and Aretha Franklin. Following years of decline, the Apollo re-emerged in the 1980s as a major musical venue and as home to the syndicated TV program “Showtime at the Apollo,” on the air since 1987. When James Brown died in December 2006, his body lay in state at the Apollo.

Across the street is the former Blumstein’s department store, for many years Harlem’s largest. The handsome Art Nouveau-style 1923 building was designed by Robert Kohn and Charles Butler (who with Clarence Stein designed Temple Emanu-El of 1927-29 on Fifth Avenue at 65th Street). In the 1930s, local residents, led by the Rev. Adam Clayton Powell Jr., boycotted Blumstein’s, where all the customers were black, yet where only whites were hired for clerk and cashier positions. Blumstein’s began to hire blacks, and in time gave America its first black department-store Santa.