Hindi is the fourth most-spoken first language in the world, after Mandarin, Spanish and English. Hindi is the third most-spoken language in the world, after Mandarin and English. On 14 September 1949, the Constituent Assembly of India adopted Hindi written in the Devanagari script as the official language of the Republic of India replacing Urdu's previous usage in British India. To this end, several stalwarts rallied and lobbied pan-India in favour of Hindi, most notably Beohar Rajendra Simha along with Hazari Prasad Dwivedi, Kaka Kalelkar, Maithili Sharan Gupt and Seth Govind Das who even debated in Parliament on this issue. As such, on the 50th birthday of Beohar Rajendra Simha on 14 September 1949, the efforts came to fruition following the adoption of Hindi as the official language. Now, it is celebrated as Hindi Day.
Here is an article on Hindi as a language of serious discourse.