Middlesex County probably was named for the English county. It was formed from Lancaster County about 1669.

Prior to 1853, when the Commonwealth began recording vital statistics, Virginia marriages were recorded at the county or city level. Beginning in 1661, in order to be married by license, the groom was required to go before the county clerk and give bond with security that there was no lawful reason to prevent the marriage. The license, issued then by the clerk, was given to the minister who performed the service. Written consent from a parent or guardian was needed for individuals younger than twenty-one years.

Until 1780, marriages could be performed only by ministers of the Established Church, who were required by law to record marriages in the parish register. In 1780, dissenting ministers (only four per county from each sect) were first permitted to perform marriage ceremonies. In order to have a record of all marriages, ministers were required to sign a certificate to be filed with the county clerk. Intially, ministers sent marriage certificates to the clerk every three months. Some ministers adopted a custom of making collected returns --a list of marriages performed within a period of time such as a year or several years. Beginning in 1784, marriage certificates were returned annually. The law was rarely enforced, and ministers' returns were sometimes late, incorrect, incomplete, and in many instances, not made at all. County clerks compiled a register of marriages based, in part, on ministers' returns.

The original returns were created by the County Court.