It was proclaimed by Governor George Grey in 1842 and named for the River Light, the river being named after Colonel William Light, the first Surveyor-General of South Australia.

[1] It covers the modern region of the Barossa Valley and a portion of the northern Mt Lofty Ranges.

[1] The county is divided into hundreds as follows: The earliest local government in the county was brought about with the establishment of the District Council of Angaston in 1853, and the District Council of Tanunda in 1855, in the south-west Hundred of Moorooroo.

By then the southernmost tip of the Hundred of Nuriootpa had been incorporated into the Town of Gawler, but it was not until the mid 1860s that further local government was established in the county.

In 1867 the District Council of Light and District Council of Nuriootpa (later called Freeling) were established to locally govern the Hundred of Light and Hundred of Nuriootpa, respectively.