Boise owes its name to French explorers who, after crossing hundreds of miles of Oregon desert, glimpsed the trees lining the Boise River and exclaimed "Les bois! Les bois!" ("The woods! The woods!"). The name stuck, slightly altered to "Boise," and the city proudly bears the nickname "City of Trees."
The municipal flag, adopted in 1989, features a blue field with a white band bearing the words "Boise | City of Trees," and in the background, a white silhouette of the Idaho State Capitol and a grove of trees. The design ranked 114th out of 150 in the 2004 NAVA survey – a mediocre score that reflects its conventional nature.
The Boise River winds through the city, lined with cottonwoods and willows, creating a verdant corridor that contrasts with the arid surrounding landscape.
In 2025, Boise made a bold political move: the city council voted 5-1 to designate three flags as official city flags – the classic municipal flag, the Pride flag, and the white organ-donor flag. In a conservative state, it was a statement of inclusion. Boise may not have the best flag in America, but it shows that a flag's meaning can evolve.