At the end of the First Burmese war in 1826, the whole of Assam gradually came under the British rule. In 1874, Assam was detached from the administrative control of Bengal and was made into a separate Chief Commissionership. As a consequent of the partition of Bengal in 1905, Assam was tagged with Eastern Bengal to form the province of Eastern Bengal and Assam under a Lieutenant Governor.

In 1912, the Chief Commissionership of Assam was revived and in 1921, Assam became a Governor's province. At the time of partition, almost the whole of the predominantly Muslim district of Sylhet was merged with East Pakistan (now Bangladesh). Subsequently, Dewangiri in North Kamrup was ceded to Bhutan in 1951. Later on, Nagaland, Meghalaya, Mizoram, and Arunachal Pradesh became separate States.

The colonial administrators maintained systematic administrative records as a guide to governance. With the formation of Chief Commissionership in Assam, a Record Branch was created under the General Department in 1874. In 1901, branch was divided into three Sections i.e. Record, Recording and Library.
In 1906, these three branches were brought under the direct control of the Registrar of the Assam Civil Secretariat. In 1949, a trained full-time Keeper of Records-cum-Librarian was appointed. This arrangement continued till 1980.

In the same year, the Government of Assam setup the State Archives as an attached office of the General Administration Department and designated it as the State Archives Organization. It became the nodal agency of the Government for matters relating to record management and administration. 

In 1996, the State Archives Organization became a full-fledged Directorate and its administrative control was transferred from General Administration Department to Secretariat Administration Department in 2006.