The USA is the second largest producer of Oranges after Brazil.
It is thought that the orange is actually an ancient hybrid of the pomelo and the tangerine.

Valencia Orange

This is one of the sweeter variaties and so is often used to produce juice.

Navel Orange

Also known as Washington, Riverside, or Bahie navel, this variant of the orange carries a (friendly) mutation which makes the oranges seedless and causes them to grow a second smaller orange opposite the stem. All Navel Oranges are clones which gives them a consistently high quality.

Blood orange

A further mutation of the navel orange causes this variety to have blood red streaks throughout the flesh. It is often used to make attractive looking marmalades.

On average, oranges have a very high acidity, close to that of table vinegar,

Other Uses

Orange peel can be used as a slug repellant (with varying degrees of success).
Orange leaves make a very nice tea.
Orange Oil derived from the pressed pith is often used in cleaning liquids.