Humewood–Cedarvale was developed in the 1910s to attract development in the growing township. Oakwood-Vaughan was also developed during this time. In the 1920s, the character of the township changed, with its southern reaches abutting the city of Toronto taking on a more urban character, compared with the very rural character of the north. The decision was made to split the township in two, with the northern, rural portion becoming North York. The remaining, two pockets of unincorporated urban development at the north end of the city, were split by the village of North Toronto, which was by then a part of the City of Toronto. Within years, the Province of Ontario saw that this arrangement was impractical, and further subdivided York, creating the township of East York out of the eastern pocket. The Township of York contracted streetcar and bus services from the Toronto Transportation Commission (later became Toronto Transit Commission in 1954), but remained independent from Toronto. During this time, American novelist Ernest Hemingway resided in the Humewood-Cedarvale community.

Vaughan Road Academy (in the Oakwood-Vaughan neighbourhood) was York's first high school. It was built in 1927 and was known as Vaughan Road Collegiate Institute until 1997, along with York Memorial Collegiate Institute at Eglinton Avenue and Keele Street in 1929.

York was part of the federation of twelve suburban municipalities that joined Toronto in 1954 to form Metropolitan Toronto. York's first and largest library, York Public Library, was built near the intersection of Eglinton Ave. and Dufferin St. in 1964, later renamed Maria Shchuka and rebuilt in 2003. In 1967, it absorbed the village of Weston, and became the Borough of York, later known as the City of York. It was amalgamated into the new City of Toronto on January 1, 1998. Since amalgamation, Maria Shchuka is part of the Toronto Public Library system.

The York Civic Centre is located at 2700 Eglinton Avenue West, between Black Creek Drive and Keele Street, near York's Museum and York Memorial Collegiate Institute.

All statistics are taken from the Canada 2006 Census.

As of 2006, more than half of York's population were foreign born. 51.8% were immigrants.

Among non-visible minority groups, the largest group in York are Portuguese people (southern half of Oakwood-Vaughan and along the whole southern part of York). St. Clair West, Rogers Road, Caledonia Road, and Dufferin Street have many Portuguese businesses. Eastern European and Jewish populations live mainly in Humewood–Cedarvale in the east end of York. There used to be a large Italian population along St. Clair West, but most have moved out to the suburbs like Woodbridge. Many Portuguese and Latin Americans live along St. Clair now. There are still many Italian businesses along the street, which is still called Corso Italia, and every year has the Corso Italia festival.

The largest visible minority group in York are Blacks who live along Eglinton Avenue West, Weston Road, and Jane Street. Several neighbourhoods had more than 30% of its population being Black such as Weston, Eglinton West, Mount Dennis, Woolner, and Oakwood-Vaughan. Many are Caribbean people with most being from Jamaica. Eglinton West is also known as Little Jamaica, home to many West Indian businesses. York also has a large Black African community with many people coming from Ghana, and Nigeria. Out of all the former cities of Toronto, York has the highest percentage of Black Canadians.

Most of the Latin Americans are from Central America. There are also a large number of people from Ecuador and Argentina. They are spread throughout York with almost every neighbourhood having a presence of Latin American people and businesses. St. Clair West is home to many Latin American restaurants and nightclubs. It also hosts many Latino festivals, including "Salsa on St. Clair" which attracts hundreds of thousands of people every year. It is Canada's biggest celebration of Latino culture. Out of all the former cities, York also has the largest percentage of Latin Americans. It is also the fastest growing minority in York, along with Filipinos, who concentrate in the eastern half of the former city. They are the fastest growing minority in York along with Latin Americans.

York also has a large Southeast Asian community, whom many are from Vietnam. They mainly live in the west end of York.