Born in Pithoragarh, Pant later became an MLA from the district. He was also a pharmacist by profession.
In February, Pant had fainted in the Vidhan Sabha while presenting the state budget for 2019-20. Thereafter, he was hardly seen in public.
Before he left for the US, Pant handed over his portfolios -- Finance and Parliamentary Affairs -- to Chief Minister Trivendra Singh Rawat, a government official said.
Pant also held the Finance portfolio in the previous BJP government in 2007-12. He was also appointed the Speaker of the interim Assembly, formed immediately after the hill state was carved out on November 9, 2000.
Expressing deep shock at his Cabinet colleague's untimely death, the Chief Minister said he had lost his younger brother. He said Pant was a dynamic leader and was always smiling.
PM Modi tweeted:
A three-day mourning has been declared in the hill state. A state holiday has also been declared on Thursday.