In 1790 the first census of the united states was taken to order of what?

In the first census, the population of the United States was enumerated to be 3,929,214. Congress assigned responsibility for the 1790 census to the marshals of United States judicial districts under an act which, with minor modifications and extensions, governed census taking through 1840.

The very first US Census was taken in 1790 in order to get the total population, to organize the United States Judicial Districts.