From Wikipedia:
"In the United States there are nine community property states: Arizona, California, Idaho, Louisiana, Nevada, New Mexico, Texas, Washington, and Wisconsin. Puerto Rico allows property to be owned as community property also. Alaska is an opt-in community property state; property is separate property unless both parties agree to make it community property through a community property agreement or a community property trust.
If property is held as community property, each spouse technically owns an undivided one-half interest in the property. This type of ownership applies to most property acquired by the husband or the wife during the course of the marriage. It generally does not apply to property acquired prior to the marriage or to property acquired by gift or inheritance during the marriage. After a divorce, community property is divided equally in some states and according to the discretion of the court in the other states.
It is extremely important to bear in mind that there are no two community property states with exactly the same laws on the subject. The statutes or judicial decisions in one state may be completely opposite to those of another state on a particular legal issue. For example, in some community property states (so-called "American Rule" states), income from separate property is also separate. In others (so-called "Civil Law" states), the income from separate property is community property. The right of a creditor to reach community property in satisfaction of a debt or other obligation incurred by one or both of the spouses also varies from state to state.
Community property has certain federal tax implications, which the Internal Revenue Service discusses in its Publication 555. In general, community property may result in lower federal capital gain taxes after the death of one spouse when the surviving spouse then sells the property. Some states have created a newer form of community property, called "community property with right of survivorship." This form of holding title has some similarities to joint tenancy with right of survivorship. The rules and effect of holding title as community property (or an another form of concurrent ownership) vary from state to state."
