what are three natural resources in Iowa?

http://kids.britannica.com/comptons/article-202872/Iowa

Three natural resources in Iowa are:

1. Agriculture: Iowa is known for its fertile soil and large agricultural industry. Corn, soybeans, and livestock are major contributors to the state's economy.
2. Coal: Iowa has significant coal deposits, which are used for electricity generation.
3. Limestone: Limestone deposits are found in various parts of Iowa and are used in construction, particularly for buildings and roads.

To find out the natural resources of Iowa, one can follow these steps:
1. Conduct an internet search using keywords such as "natural resources of Iowa."
2. Explore official websites, such as those of Iowa state government or environmental agencies, as they often provide lists or detailed information about the state's natural resources.
3. Consult academic resources, such as online research publications or books about Iowa's geology or agriculture.
4. Visit local libraries or contact experts in the field, such as agricultural or geological departments at universities, who can provide valuable information.