Nebraska was one of the last states to adopt a State Flag. Representative J. Lloyd McMaster introduced a bill in 1925 to designate a state banner. The bill was passed - the law describes the banner as "a reproduction of the Great Seal of the State charged on the center in gold and silver on a field of national blue." In 1963 the Legislature finally designated the state banner as the official flag of Nebraska.

The symbols on the great seal of Nebraska are described on a bill introduced in 1867:

"The eastern part of the circle to be represented by a steamboat ascending the Missouri River, the mechanic arts to be represented by a smith with a hammer and anvil, in the foreground, agriculture to be represented by a settlers cabin, sheaves of wheat, and stalks of growing corn, in the background a train of cars heading towards the Rocky Mountains, and on the extreme west, the Rocky Mountains to be plainly in view, around the top of the circle, to be in capital letters, the motto: "Equality Before the Law," and the circle to be surrounded with the words, "Great Seal of the State of Nebraska.

Source:

History of the Nebraska State Flag: Nebraska SOS
The Great Seal of Nebraska: Nebraska SOS

Links:

Nebraska State Symbols: Nebraska Secretary of State
State Flags - 50 states List
National Flag