Researchers can use the Federal Census to place their ancestors in a specific locality. Once it is known where they lived,  genealogists can look to land and courthouse or vital records for more clues.

Here is a list what information has been included in each census:

1790
head of household by name
number of free white males
number of slaves

1800
head of household by name
free white males by age groups
free white females by age groups
number of slaves

1810
head of household by name
free white males by age groups
free white females by age groups
number of slaves

1820
head of household by name
free white males by age groups
free white females by age groups
number of slaves
number of male and female slaves by age groups
number of foreigners (NOT naturalized citizens)

1830
head of household by name
free white males by age groups
free white females by age groups
number of slaves
number of male and female slaves by age groups
number of foreigners (NOT naturalized citizens)
number of deaf, dumb, blind by categories

1840
head of household by name
free white males by age groups
free white females by age groups
number of slaves
number of male and female slaves by age groups
number of foreigners (NOT naturalized citizens)
number of deaf, dumb, blind by categories
whether receiving federal military pension
whether attending school

1850
all household members by name
sex
color
birthplace
occupation
value of real estate
whether married within the year
deaf, dumb, blind, insane
whether a pauper
whether a convict
whether able to read, write
whether attended school during last year

1860
all household members by name
sex
color
birthplace
occupation
value of real estate
value of personal property
whether married within the year
deaf, dumb, blind, insane
whether a pauper
whether a convict
whether able to read, write
whether attended school during last year

1870
all household members by name
month of birth if born during last year
sex
color
birthplace
occupation
value of real estate
value of personal property
whether married within the year
month of marriage if married during last year
deaf, dumb, blind, insane
whether able to read, write
whether attended school during last year
whether father or mother of foreign birth

1880
all household members by name
street name and house number
relationship to head of family
month of birth if born during last year
sex
color
birthplace
occupation
marital status
whether married during last year
whether disabled
whether crippled, maimed or deformed
time unemployed during census year
deaf, dumb, blind, insane
whether able to read, write
whether attended school during last year
birthplaces of father and mother
whether father or mother of foreign birth

1890
only 6% available because of fire damage

1900
all household members by name
street name and house number
relationship to head of family
month of birth if born during last year
sex
color
birthplace
occupation
whether naturalized and when
number of years in US
whether home, property mortgaged
marital status
time unemployed during census year
whether able to speak English
whether able to read, write
whether attended school during last year
birthplaces of father and mother
whether father or mother of foreign birth
number of living children if a woman
whether soldier, sailor or marine during Civil War 
(Union or Confederate) or widow
number of years in present marriage
number of children born

1910
all household members by name
street name and house number
relationship to head of family
sex
color
birthplace
occupation
whether naturalized and when
number of years in US
whether home, property mortgaged
marital status
time unemployed during census year
whether deaf, dumb, blind or insane
whether able to speak English
whether able to read, write
whether attended school during last year
birthplaces of father and mother
whether father or mother of foreign birth
number of living children if a woman
whether soldier, sailor or marine during Civil War (Union of Confederate) or widow
number of years in present marriage
number of children born
mother tongue

1920
all household members by name
street name and house number
relationship to head of family
sex
color
birthplace
occupation 
whether naturalized and when
number of years in US
whether home, property mortgaged
marital status
whether deaf, dumb, blind or insane
whether able to speak English
whether able to read, write
whether attended school during last year
birthplaces of father and mother
whether father or mother of foreign birth
number of children born
mother tongue
mother tongue of father
mother tongue of mother
year of naturalization