These records kept by the government about the former occupants of your house can tell you who lived in your house, what their occupations were, what valuables they possessed, and other important clues.
Assessment records are the records of the taxable holdings of property owners, on which local taxes were based. Taxes were collected locally for such purposes as financing public schools. In order to base the taxes on the value of the property, tax assessors went door to door recording information on the owner's holdings, such as land, buildings, and outbuildings. In some years, only a monetary value was recorded, but you may find years when buildings, livestock, slaves, and other taxable property was listed. These public records are available for a wide range of years, from the late eighteenth century to the 1940s.
How to use? Look up the homeowner's name (under the first letter of the last name) in the hundred where the home is located. As with other records, you are looking for changes over time. Here, the change may be an increase in tax value from one assessment year to another. Such an increase could mean that a house was built. Or, the rise in value could refer to the construction of an addition or other improvement. It is useful to link the assessment information with other facts about the occupants. Have the occupants recently married? Is their farm producing exceedingly well? Such information assists when making a conjecture that an increase in the assessed value indicates the date of an addition.
Available at DSA. Some holdings at HSD, UD
Census records are Federal documents that record information on the population of the United States at ten-year intervals. You can find information relevant to a house's history in the population census, including statistics on the property owner, the head of the household, the occupants of the house and their ages, occupations of the residents (including slaves or servants), race of occupants, and country of origin.
If your house was part of a farm, the Agricultural Census can provide you with information on the type of farming that was carried out on the property, including numbers of livestock, crops raised, and farm buildings. Another kind of census record is the Census of Industry. If your property was connected with some type of industry, such as milling or blacksmithing, you should also look at these records.
What census documents are available in Delaware? The first Federal population census was conducted in 1790. Delaware's census records for 1790 are missing and believed to have been destroyed during the War of 1812 when the British invaded Washington, D.C. (Instead, see Leon De Valinger, Reconstructed 1790 Census of Delaware. Wash. D.C.: National Genealogical Society, 1954. At UD: Ref. HA 296 .D481954.) Delaware's census records for 1890 have also been lost. Population census records up to 1920 have been released and are available for Delaware. Delaware's Agricultural Census and Census of Industry are available for the third quarter of the nineteenth century. Until about 1850, the information collected by census takers varied considerably. You will find more consistency in later records.
How to use? It is necessary to know what hundred a person lived in to find that person in census records. What you want to use are the enumeration schedules for the population census. These schedules give you the detailed information recorded by the census taker at each house visited. They are not in alphabetical order, but are in the order of the houses visited by the census taker for each hundred. However, there is an easy way to find the person you are researching in the enumeration schedules. Indices have been created for census years 1800-1870. These are in separate bound volumes. All you have to do is look up the name of the individual in the index, jot down the reference number, and then go to the census records on microfilm. The Agricultural Census and Census of Industry are also organized by hundred.
Population Census available at DSA, HSD, UD (microfilm S550). Population Census indices at UD (Ref. F 163.J33).
Census of Industry and Agricultural Census for 1850-1870 availlible at DSA, HSD.