Waterloo is a city in Southern Ontario, Canada. It is the smallest of the three cities in the Regional Municipality of Waterloo, and is adjacent to the city of Kitchener. Kitchener and Waterloo are often jointly referred to as "Kitchener-Waterloo", "KW", the "Twin Cities" or "the Tri-City". Years ago, there had been several attempts to combine the two cities into one but they were not successful. After 1973, when the Regional government was formed, there was less motivation to do so.