There are only four ingredients in Morton's Iodized salt.
Salt- This one is quite obvious, couldn't have salt without salt! Salt is made in salt farms, letting water from the sea evaporate so just salt is left behind. It is the words most common seasoning.
Calcium Silicate- This is a power that comes from limestone. It is also used in roads, bricks and cements! But don't worry, it will not harm us in any way, and is used in salt to stop it forming into clumps, so will come out the salt shaker nice and easily.
Sugar- This seems quite unexpected to me, why would there be sugar in salt? Only iodized salt will contain sugar as it stops it from oxidizing. There is such a small amount in it however that it is not considered relevant.
Potassium Iodide- This is sprayed on the salt before it is packaged. It is added as a safety factor.