The population of Northampton is about 212,000 people according to official census data released on Monday morning.
Northamptonshire has about 692,000 people currently living here, the data suggests.
The numbers are significant to the county as Government allocations of money are based on population estimates.
The census was taken in 2011 and organisers believe it is still the most comprehensive snapshot of life in towns and cities. They claimed the latest survey saw a 95 per cent completion rate across the England and Wales.
Numbers of pensioners in the county are also a great worry for the NHS and Northamptonshire County Council who must plan how to care for them in greater numbers and greater proportions of the general population.
The 2011 census reveals there were 106,000 people 65 or over in the county, 4,700 of who were 90 years-old or older.
In Northampton, 28,200 people were aged 65 or over, with 1,400 aged 90 or over.
Households, generally the number of occupied flats or houses, were up to 287,700 in across the county compared to 259,066 at the time of the last census in 2001.
In Northampton there were 88,700 households in 2011 compared with 80,822 in 2001, a rise of about 9.7 per cent over a decade.
Census bosses are releasing the data in stages. Figures for religion, marital status, country of birth, ethnicity and health will be revealed in November, followed by two further releases in 2013