The Zillertal branches off from the Inntal near Jenbach, about 40km northeast of Innsbruck, running mostly in a north-south direction. The Zillertal proper stretches from the village of Strass to Mayrhofen, where it separates into four smaller valleys, the Tuxertal and the sparsely settled, so-called Gründe - Zamsergrund, Zillergrund and Stilluppgrund. Along the way, two more Gründe and the Gerlostal, which leads to the Gerlos Pass and into Salzburg, branch off.
Unlike other side valleys of the Inntal, the Zillertal rises constantly, but only marginally, from one end to the other - only about 100 m over 30 km. Permanent settlements cover about 9% of the entire area of the Zillertal municipalities.
Near the Tuxer Joch, a pass between the Wipptal and the Tuxertal, there have been archeological finds from middle Stone Age. The oldest remains of settlements in the Zillertal date back to the Illyrians during the late Bronze and early Iron Ages - a tribe from the Balkan Peninsula who were absorbed by the Bavarians (Baiuvarii).
The earliest written record of the Zillertal dates from 889, when Arnulf of Carinthia granted land to the Archbishop of Salzburg in the "Cilarestal". Ownership of the valley was divided along the river Ziller. Even today this division is visible, as churches on the right bank of the river generally have green towers and belong to Salzburg Diocese, while churches on the left bank have red towers and belong to Innsbruck Diocese.
In 1248 the land west of the Ziller was acquired by the Counts of Tyrol, while the lands east of the Ziller pledged as security to the Counts of Tyrol by the Lords of Rattenberg from 1290 to 1380. In 1504, with both the County of Tyrol and the Archbishopric of Salzburg dominated by the Habsburgs, the Zillertal valley was united under Emperor Maximilian and put under joint Tyrolean/Salzburgian rule.
In 1805, the Treaty of Pressburg ended the War of the Third Coalition and forced Austria to cede Tyrol to Bavaria. For the purposes of this treaty, the Zillertal was considered part of Salzburg and thus remained with Austria. The people of the Zillertal nevertheless joined Andreas Hofer's Tyrolean Insurrection of 1809 in the Battle of the Ziller Bridge (14 May). Later that year, the insurrection was defeated and the Zillertal briefly became Bavarian until the Congress of Vienna in 1814/1815.
While the relatively lenient stance of the archbishops of Salzburg had allowed the creation of small pockets of Protestantism in their lands since the Protestant Reformation, the remaining Protestants were oppressed more harshly during the Habsburg rule of the 19th century. In 1837, 437 Protestant inhabitants of the Zillertal left the valley after they were given the choice of renouncing the Augsburg Confession or emigrating to Silesia, where Frederick William III of Prussia offered them lands and housing near Erdmannsdorf (now Myslakowice in western Poland).
In 1902, the Zillertalbahn railway was constructed, which still runs between Jenbach and Mayrhofen to this day, opening up the valley, the economy of which had previously relied mostly on agriculture and mining, to commerce and tourism. From 1921 to 1976, magnesium carbonate (and later tungsten) were mined around the Alpine pastures of the Schrofen and Wangl Almen above the Tuxertal A ropeway conveyor of more than 9 km length was used to transport the ore to the Zillertalbahn cargo station in the valley below.
With the downfall of the mining industry in the valley, tourism has become the dominant economical factor in the second half of the 20th century and beyond. There are now (as of 2003) 6 million nights spent by tourists in the valley, mostly during winter sports holidays. Following a phase of mergers by building connecting lifts during the 1990s and early 2000s, there are now four big ski areas and three smaller satellite areas in the valley, with a combined total of more than 170 lifts and more than 630 km of downhill slopes.
Traditional agriculture - mostly cattle, dairy and some sheep farming on the Alm pastures - is still widespread, securing the continued existence of this predominant cultural landscape. There is also a significant lumber industry with a large sawmill outside the village of Fügen, and a relatively large number of factories of various industries in the outher valley. Four large reservoirs in the Gründe supply the water for a total of eight hydroelectric power stations generating slightly more than 1,200 GWh per year.