If I don't know my family medical history, what is the best time to begin having mammograms?

Age Forty. There is currently a debate whether to begin mammography at 40 or 50. The controversy is that, in order for a screening test to prove beneficial, it has to decrease the mortality rate of those that have the test. While mammograms conclusively diagnose breast cancers earlier beginning at age 40, the mortality rates are less clear. When weighing the pro's and con's, I am a strong proponent.
Mammo. According to the American Cancer Society, American College of Radiology, and others, annual screening mammography should begin at age 40. Screening may begin sooner if you are a BRCA carrier or are otherwise at high risk. If you don't know your family history, probably should treat yourself as average risk and start at 40.
40. At this time screening, yearly mammograms should begin at age 40 years. If there is a first degree family history, risk assessment is important. The screening mammogram controversy emphasizes the need for individualized care, rather than making blanket recommendations..