Catastrophe losses in 2011 will reach the $1 billion mark for American Family Insurance.

The Madison, Wisc.-based insurer of homes, automobiles, businesses and farms says it has paid about $100 million to victims of a destructive tornado in Joplin, Mo. last May.

The Joplin tornado destroyed 400 homes and damaged hundreds of others. Policyholders filed 2,300 property, auto and commercial claims.

Severe-weather events heavily affected many of the insurer’s top states for business, according to Highline Data, a part of Summit Business Media, publisher of NU.

About 15.3 percent of American Family’s direct-premiums written come from Missouri. Other than the Joplin twister, a tornado in St. Louis and a windstorm in Kansas City—both in April—generated more than 21,000 claims and claim payments of $28.5 million and $76.4 million, respectively.

The insurer’s home state is its top state for business, accounting for nearly 17 percent of its direct-premiums written. La Crosse, Wisc. saw a tornado in May, and hailstorms have also hit different parts of the state.

According to Highline Data, American Family was the top homeowners’ insurer in Wisconsin with a 22.9 percent market share.

In Missouri, American Family is second to State Farm for homeowners’ insurance with a 16.7 percent market share.

As of July 31, American Family has paid $963.5 million in claims and expects the total to reach $1 billion after payments in August.

This is the third year American Family has reached the $1 billion mark in catastrophe losses. The other years were in 2006 and 2008.

The insurer says it paid out $906.3 million for claims in 2010.