Community interest expressed in fall 2019 has led the Town to explore the possibility of a future sister city relationship for Castle Rock. Sister city partnerships can have cultural, educational, business or civics purposes.
A committee met in early 2020 and determined the goal should be to locate a sister city within one of five countries: Belgium, Germany, Ireland, Italy or Japan. In April 2020, more than 1,000 social media responses helped focus the group's efforts on finding a sister city in Ireland. Now, Sister Cities International is working on the Town's behalf to make that goal a reality.