The kingdom of Pagan, the "charter polity" of Burma, had a lasting impact on Burmese history and the history of mainland Southeast Asia. The success and longevity of Pagan's dominance over the Irrawaddy valley enabled the ascent of Burmese language and culture, and the spread of Burman ethnicity in Upper Burma and laid the foundation for their continued spread elsewhere in later centuries. The 250-year rule left a proven system of administrative and cultural norms that would be adopted and extended by successor kingdoms—not only by the Burmese-speaking Ava Kingdom but also by the Mon-speaking Hanthawaddy Kingdom and Shan-speaking Shan states.