The tidal flats in the south are noted for endangered horseshoe crabs and the sea area between Kōnoshima and Nishi-Oshima has been designated as a national Natural Monument.

The Mizuno invested vast sums of money in civil engineering projects to promote the development of new rice fields in Kasaoka, which originally had little flat land.

Following the Meiji restoration, the village of Kasaoka was established within Oda District, Okayama with the creation of the modern municipalities system on June 1, 1889.

Due to its strong historical, cultural and economic ties with Fukuyama, proposals have been made for a merger between the two municipalities.

Kasaoka has a mayor-council form of government with a directly elected mayor and a unicameral city council of 17 members.

In terms of national politics, the city is part of the Okayama 3rd district of the lower house of the Diet of Japan.

Agriculture, food processing are also major contributors to the local economy, although the traditional industries stone quarrying and production of pyrethrum are in decline due to competition from foreign sources.