In the Selkirk Mountains, at the confluence of the Kootenay and Columbia Rivers, it is a regional trade and transportation centre, with a local economy based on forestry, mining and tourism.

Castlegar is home to Selkirk College, a regional airport, a pulp mill, and several sawmills.

Outside the city limits are the small surrounding communities of Ootischenia, Brilliant, Robson, Robson West, Raspberry, Tarrys, Thrums, Glade,[4] Shoreacres, Fairview, Genelle, Pass Creek and Krestova, and the much smaller communities of Deer Park, Renata, and Syringa on Lower Arrow Lake.

On 5 September 1811, David Thompson arrived in the area of present-day Castlegar, and camped near the mouth of the Kootenay River.

Experts cannot agree where one band's range ended and the other's began, as there was much overlapping of cultural and territorial activity between them.

Most recent information suggests that the Sinixt were the area's original people, and that the Kootenai arrived several hundred years ago from central Canada.

A reconstructed kekuli dwelling was discovered on Zuckerberg Island, at the confluence of the Kootenay and Columbia rivers.

The Doukhobors operated a ferry near Brilliant on the Kootenay River in 1910, and the Christian Community of Universal Brotherhood (CCUB) applied to CPR for a railway station and siding to that point.

Castlegar is wetter than most places in the Southern Interior of BC, and the city receives around 400 mm more precipitation than nearby Kelowna, Penticton and Kamloops (which are in the drier Okanagan region of British Columbia, while Castlegar is in the Kootenay region).

Along the river to the west are Scotties Marina and Syringa Provincial Park, with boating and camping amenities.

The city's collegiate hockey team is the Selkirk College Saints of the BCIHL, who, as of 2016, are four-time defending league champions.

Castlegar's main business street, Columbia Avenue, runs the length of the city.

There are several neighbourhoods in Castlegar, including Downtown, Southridge, Oglow Subdivision, Woodland Park, Grosvenor, Kinnaird, and Blueberry Creek.

Highway 3 bisects Castlegar, providing the main access to the Grovesnor area, and crossing the Columbia River at the Kinnaird Bridge, to Ootischenia.