Kansas recognized the sunflower as official state flower and floral emblem in 1903 (the sunflower is also featured on the Kansas state quarter, state flag, and the nickname for Kansas is The Sunflower State. Excerpt from Kansas legislation:

WHEREAS, Kansas has a native wild flower common throughout her borders, hardy and conspicuous, of definite, unvarying and striking shape, easily sketched, moulded, and carved, having armorial capacities, ideally adapted for artistic reproduction, with its strong, distinct disk and its golden circle of clear glowing rays -- a flower that a child can draw on a slate, a woman can work in silk, or a man can carve on stone or fashion in clay; and

WHEREAS, This flower has to all Kansans a historic symbolism which speaks of frontier days, winding trails, pathless prairies, and is full of the life and glory of the past, the pride of the present, and richly emblematic of the majesty of a golden future, and is a flower which has given Kansas the world-wide name, "the sunflower state"...

More Info: www.statesymbolsusa.org