Probably Beijing, in the early nineteenth century. Earlier million-cities have been claimed, but capitals seem rarely to have exceeded half a million.
__________
According to my knowledge and information its "Hangzhou" is the first Chinese city to reach 1 million populations. After Hangzhou Beijing, Guangzhou cities are ranking for their population.
___________
As I said, capitals before the 19th century rarely exceeded half a million. Hangzhou is one such. The walls enclosed fewer than 30 sq km before the 15th century, 40 afterward, and the city was said to be of low-rise construction, pointing to a population around 500,000. High early household estimates are likely to relate to a far wider county population (this was still going on in the 19th century too, hence I suspect some of the very high figures for even Beijing). Guangzhou's walled area was far smaller, but is said not to have encompassed the whole city: early returms indicate something of the order of 300,000 inhabitants for the whole, rising sharply in the 19th century; whether it reached a million even then is questionable, but Beijing was already there.
C.e 1650
1880
The population of England in 1950 was 50 million people. It is estimated that by the year 2039 the population of England will reach 70 million people.
Black death affected Europe from about 1340 onwards. It killed large population of Europe, almost 100 million people died of this deadly disease. It reduced worlds population from 450 million to 350 million.
1811
The first state population to reach 10 million was New York. This milestone was reached in the early 20th century, reflecting the state's significant growth and urbanization during that time.
Rome
The population first reached 1 million in 1908.
1927
1999
C.e 1650
400 million
The United-States population reached 100 million in 1920, 200 million in 1967, and 300 million in 2006. It's projected to reach 400 million in 2038, 500 million in 2066, 600 million by 2100, and 1 billion by 2200.
Rome was the first city to have one million inhabitants, and this occurred in 133 BC. The second city to reach the one million mark was Alexandria, Egypt in 30 BC.
By 2010, Jordan's population is expected to reach up to 7.1 million.
According to the Australian Bureau of statistics, Australia's population reached thirteen million in March 1971.
London