[6] The neighborhood has one of the largest Hispanic communities in New York City, mostly Puerto Ricans, as well as Dominicans, Cubans, and Mexicans.

The extension of cable cars up Lexington Avenue into East Harlem was stymied by the incline created by Duffy's Hill at 103rd Street, one of the steepest grades in Manhattan.

[15] East Harlem consisted of pockets of ethnically sorted settlements – Italian, German, Irish, and Jewish – which were beginning to press up against each other, with the spaces still between them occupied by "gasworks, stockyards and tar and garbage dumps".

[15] In 1895, the Union Settlement Association, one of the oldest settlement houses in New York City, began providing services in the area, offering the immigrant and low-income residents a range of community-based programs, including boys and girls clubs, a sewing school and adult education classes.

[3] After becoming mayor, La Guardia helped plan a large expansion of Thomas Jefferson Park at First Avenue, between 111th and 114th Streets, in the mid-1930s.

[17] The fabric of the Italian-American community was torn when, after the Second World War, the unhealthy tenements started to be demolished and replaced with better housing, forcing families to relocate.

Today, the few remaining Italian-American residents in Harlem are predominantly older, clustered around Pleasant Avenue and the Our Lady of Mount Carmel Church, mainly from 114th to 118th Streets and the surrounding area.

[3] The newly dominant Puerto Rican population, which reached 63,000 in 1950, continued to define the neighborhood according to its needs, establishing bodegas and botánicas as it expanded; by the 1930s[24] there was already an enclosed street market underneath the Park Avenue railroad viaduct between 111th and 116th Streets, called "La Marqueta" ("The Market").

[14] Until 2006, property values in East Harlem climbed along with those in the rest of New York City, leading to gentrification and changes to area demographics.

[4] Beginning in 2016, the New York City government was seeking to rezone East Harlem "to facilitate new residential, commercial, community facility, and manufacturing development".

[2] Based on data from the 2010 United States Census, the population of East Harlem North was 58,019, an increase of 871 (1.5%) from the 57,148 counted in 2000.

Increasing rents in Lower Manhattan's Chinatown have driven many into public and subsidized housing developments in the neighborhood.

[7][8][9] Social problems, including concentrated poverty, homelessness, overcrowding, substandard housing, language barriers, food insecurity, teen pregnancy, obesity, crime, drug addiction, dropping out of school, and low rates of advanced educational attainment, have long plagued the area.

[48] Union Settlement Association is one of the neighborhood's largest social service agencies, reaching more than 13,000 people annually at 17 locations throughout East Harlem, through a range of programs, including early childhood education, youth development, senior services, job training, the arts, adult education, nutrition, counseling, a farmers' market, community development, and neighborhood cultural events.

East Harlem is dominated by public housing complexes of various types, with a high concentration of older tenement buildings between these developments.

[49][50] After a wave of arson ravaged the low income communities of New York City throughout the 1970s, many of the residential structures in East Harlem were left seriously damaged or destroyed.

By the late 1970s, the city began to rehabilitate many abandoned tenement style buildings and designate them as low income housing.

PRdream.com, a web site on the history and culture of Puerto Ricans, founded a media gallery and digital film studio called MediaNoche in 2003.

It presents technology-based art on Park Avenue and 102nd Street, providing exhibition space and residencies for artists and filmmakers, and webcasting events.

[63] The Willis Avenue Bridge which connects East Harlem to the Mott Haven section of the Bronx has long been a hotspot for robbery.

In 2018, this population of uninsured residents was estimated to be 3%, slightly less than the citywide rate of 12%, though this was based on a small sample size.

[40]: 14 The concentration of fine particulate matter, the deadliest type of air pollutant, in East Harlem is 0.0082 mg/m3 (8.2×10−9 oz/cu ft), more than the city average.

Citizens of East Harlem are likely to buy food from grocery stores that have a limited supply of fruits and vegetables, which are often of poor quality and generally more expensive than the same products sold at supermarkets.

[78] Without access to affordable produce and meats, East Harlem residents have difficulty eating a healthy diet, which contributes to high rates of obesity and diabetes.

[79] In 2011, Manhattan Borough President Scott Stringer announced a program which would send Veggie Vans to East Harlem senior centers and housing projects.

In 2013, a new Super FI Emperior Grocery store opened up in East Harlem on 103rd Street and Lexington Avenue.

[40]: 6  The percentage of East Harlem students excelling in math rose from 25% in 2000 to 51% in 2011, and reading achievement increased from 33% to 39% during the same time period.

[87] East Harlem's rate of elementary school student absenteeism is higher than the rest of New York City.

[41]: 24 (PDF p. 55) [40]: 6  Additionally, 67% of high school students in East Harlem graduate on time, less than the citywide average of 75%.

[131] Metro-North Railroad has a commuter rail station at Harlem–125th Street, serving trains to the Lower Hudson Valley and Connecticut.