Twin towns or sister cities are a form of legal and social agreement between towns, cities, counties, oblasts, prefectures, provinces, regions, states, and even countries in geographically and politically distinct areas to promote cultural and commercial ties. The modern concept of town twinning, conceived after the Second World War in 1947, was intended to foster friendship and understanding between different cultures and between former foes as an act of peace and reconciliation, and to encourage trade and tourism. In recent times, town twinning has increasingly been used to form strategic international business links between member cities.(Wikipedia)
"LA Sister Cities"
"Sister Cities of LA"