Rockdale, four miles south of Mt. Upton, was settled very early. The first settlers were James and Rubus Phelps. To build their cabins and wells they had to blast the underlining rock ledge 12 feet down and hence the name of the hamlet. A bridge was built across the river in 1799 which was the first bridge across the Unadilla River.
In the 1800's it contained one church(Union), one district school, one hotel , a saw and grist mill, one store, a creamery, a carriage shop, and a blacksmith shop, two shoe shops, and a population of 80.
The first merchant was Gaius Boughton in 1814. The first postmaster was Isaac Cox who was appointed in 1829. The first physician was James Secor who came from Mt.Upton in 1847.
The saw and grist mill was built in 1809 by Samuel Cotton and Joseph Gilbert. The Rockdale Creamery was built in the spring of 1865. The Rockdale Religious Society was organized in 1859.