A 30 year fixed-rate mortgage hasn't always been the standard. As part of FDR's New Deal in 1934, the Federal Housing Administration was created to help Americans purchase homes with affordable terms.
Prior to then, many loans had an amount due at the end of the term called a balloon. Most mortgages had adjustable interest rates even though some might be fixed for a short time. While banks would loan money on a home, they retained the right to call the note due at any time which could exert considerable stress on borrowers.
FHA, during this time, introduced mortgages that offered a fixed rate of interest to the borrower for a 30 year term. This fully amortized loan provided borrowers a financial vehicle that would help them achieve the American Dream while minimizing the risk of having a loan called without the resources to pay it off. It brought long-term stability to the housing market and helped stimulate the economic recovery at a very difficult time in our nation's history.
Roughly, a third of the mortgages created in 2011 were less than 30 year terms. Many homeowners, similar to those after the Great Depression, would like to get their home paid for as soon as possible. Shorter term mortgages typically have a lower interest rate but higher payments due to fewer years to amortize the mortgage.