The great seal of New Jersey was originally designed by Pierre Eugene du Simitiere in 1777 and has had only minor changes made since then. Symbols on the state seal represent:

Three plows on the shield honor the state's agricultural tradition. The helmet above the shield faces forward, an attitude of sovereignty and thus particularly fitting for one of the first governments created under the notion that the state itself is the sovereign. The crest above the helmet is a horse's head (the horse is also New Jersey's official state animal).

The supporting female figures are Liberty and Ceres (Roman goddess of grain - a symbol of abundance). Liberty carries the liberty cap on her staff and Ceres holds a cornucopia filled with harvested produce. A banner below contains the state motto "Liberty and Prosperity" and the date of New Jersey statehood: 1776.

Originally Liberty held her staff in the crook of her arm rather than her right hand. The female figures now face straight ahead but once looked away from the shield. The cornucopia that Ceres holds upright was once inverted, its open end upon the ground. In 1928 the year of statehood (1776) first appeared in Arabic figures. The state flag also features the state seal of New Jersey:

Source:

The Great Seal of the State of New Jersey: NJ.gov

Links:

State Seals - 50 States List
National Seal