Alta has been inhabited for a long time, as evidenced by the rock carvings that are believed to be around 7000 years old.

Before the 18^th century, Alta was largely inhabited by the Sea Sami who lived from hunting, fishing, and animal husbandry. The area was a common tax area for Denmark-Norway, Sweden, and Russia. Sweden and Denmark had arguments about who had the right to tax salmon fishing in the Alta River, so the Danes built a fortress. At the peace of Knaerød in 1613, the area was given to Denmark-Norway. This is when the first Norwegians began to inhabit the area. The Kvens began to arrive in 1700 because of war and famine, and the Kven brought grain cultivation and improved river fishing methods.

In 1826 the English company Alten Copper Mines started mining in Kåfjord. Many miners came from Scandinavia and during the mining period this was the most populous place in Finnmark. However, operations closed in 1878.

In the 19^th century, the Pomor Trade was important for the area around Alta. Norwegian fish was exchanged for Russian grain and supplied the coastal population in large parts of Norway.

During World War II, Alta was a key strategic location for German forces. The battleship Tirpitz was based in the Altafjord for two years and served as one of the main threats against convoys delivering supplies from Western Allies to the Soviet Union. Alta was burned down by the Nazis in the autumn of 1944 during their retreat. The only building not to be burned down was the Alta church.

In the late 1970s and early 1980s there was a series of protests in Finnmark against the construction of a hydroelectric powerplant in the Alta River. Known as the Alta Controversy, it put the rights of the Sami as an indigenous people, with distinct rights over the lands in northern Norway, onto the national political agenda. For the first time since World War II, Norwegians were arrested and charged with violating laws against rioting. Two Sami women even travelled to Rome to petition the pope.

The Supreme Court ruled in favour of the government in early 1982, at which point organised opposition to the powerplant ceased, and the power plant was built. However, it is considered that although the Sami lost this particular issue, they made important long-term gains.