Deb Haaland has become the first Native American woman to govern a US state, following her victory in Wednesday's midterm elections.

Ms Haaland, 65, a member of the Laguna Pueblo tribe, defeated Republican opponent Gregg Hull, 60, with the Associated Press (AP) calling the result midway through the afternoon (AEDT).

The former Interior Secretary under Joe Biden was the United States' first Indigenous cabinet secretary and will govern a state where Native Americans make up 12 per cent of the population.

Throughout her campaign, Ms Haaland — whose father won a Silver Star in the Marine Corps for his actions in Vietnam — highlighted the difficulties of navigating Medicaid as a single mother before attending law school in her 30s.

She was also open about her struggles with addiction, telling The Guardian this year: "I guess I'm like so many New Mexicans. I started abusing alcohol at a young age and I was very fortunate that, at the age of 23, I recognised that I wanted to live a sober life and so I went on that journey and worked on myself for quite a while.

"It's a lot of hard work to pay attention to yourself. I recognised there were so many things in my life that I needed to change."

Ms Haaland was the first Native American woman to be elected to lead a state party. Alongside Kansas representative Sharice Davids, they became the first Native American women elected to Congress in 2018.

The Midterms had the highest number of Indigenous candidates ever, according to a database by ICT and Advance Native Political Leadership, with over 225 candidates running in 30 different states in total.

The candidates represent nearly 100 different Indigenous nations that are state or federally-recognised in the United States, others are Indigenous communities from across borders.