Fannie Mae was chartered in 1938, as the Federal National Mortgage Association (FNMA), with the responsibility of creating a secondary market for home mortgages. It operated under direct federal control. In 1968, the Federal National Mortgage Association was partitioned into two separate entities- one wholly owned by the government and known as the Government National Mortgage Association (Ginnie Mae), and the other to retain the Federal National Mortgage Association (Fannie Mae) name. It was privatized by legislation enacted in 1968 and became fully private in 1970.

Fannie Mae (along with Freddie Mac) sets the limit each year on the size of a conforming loan based on the October to October changes in mean home price. Mortgages above this limit are considered jumbo and super jumbo loans because Fannie Mae and Freddie Mac only buy conforming loans to repackage into the secondary market, making the demand for non-conforming loans much less. Thus, interest rates for jumbo and super jumbo loans are higher than for conforming loans.

According to the Office of Management and Budget (OMB), borrowers see mortgage rates 25-50 basis points lower because of what Fannie Mae and Freddie Mac do. This is reflected in lowered interest rates of up to a half percentage on each individual homebuyer's mortgage, which translates to lower payments and increased consumer cash flow for other purposes. Fannie Mae and Freddie Mac also were the agencies that recommended that FICO scores be used in mortgage lending. Now, FICO scores are the mortgage industry standard for originating conventional loans, adjustable rate mortgages (ARMs) based on various prime rate indices, jumbo loans and 2nd home purchases as well as the popular cash out mortgage refinance loans.

Today, Fair Isaac estimates that more than 75% of all mortgage originations in the U.S. involve the FICO credit score. FICO scores are being used in almost every sector of the nation's economy, and largely determine whether or not you will be approved for credit (including mortgage loans), what interest rates you will pay and what loan terms are available to you. This is why it is important to maintain a high FICO. But, if you're a homeowner who's had credit issues in the past, a timely mortgage refinance or home equity loan (second mortgage) for debt consolidation can help raise your score substantially and save you a lot of money.