Siheung is a city in Gyeonggi Province, South Korea. The city has a population of 511,807 people, where 508,646 are residents out of 218,846 households as of August 2021. Siheung acquired its current administrative structure on January 1, 1989, the former Siheung County was divided into the cities of Siheung, Gunpo, and Uiwang. At the time, Siheung had a population of only 93,000. This number more than tripled in the following decade as massive suburban apartment complexes were developed. Today's Siheung city area formerly belonged to Incheon and Ansan before 1914.

Oido (Korean: 오이도) is an island on the West Coast region of South Korea's Gyeonggi Province. It is an area of Siheung stretching from north to south with low hills under 72.9 m (239 ft). Oido has shell mounds throughout the whole area, with the largest of the mounds located on the West Coast. The Oido shell mounds are the only remains of the exchanges between the North and South Neolithic cultures of the Korean Peninsula. The mounds also provide information on the Neolithic area's changing coastal environment.