The amount of freely available data on infant mortality is incredible. Keep in mind there can be problems related to lack of consistency in how the data was collected which could compromise accuracy. But even given these limitations, the available data is impressive and useful.
We have observed numerous websites which share statistics on SIDS deaths, but outside of state Child Fatality Review reports, most ultimately link back to one main source, the Centers for Disease Control (CDC). If you are looking for raw data, in what we have seen, the CDC is your best source.
Centers for Disease Control (CDC)
The Centers for Disease Control (CDC) is the keeper of something called the National Vital Statistics. The CDC publishes annual reports summarizing things like the number of births and deaths in a given year. These are massive data rich documents, and they take a little time to consume, but the information is very good. For instance, this is where you can see there were 2,437,163 total deaths in the US during 2009 including 26,412 infants, and that 2,226 were classified as SIDS. In our experience, this is where you find most of the original source data on the number of SIDS deaths per year. Click here to gain access to this information: Once you get to the page look for documents titled Deaths: Final Data for 2009. NVSR Volume 60, Number 03. 117 pp. (PHS) 2012-1120. This particular document is for deaths that occurred in 2009, see page 12 for the section on infant mortality. There is one of these summary documents for every year going back to 1996. Click here for tables that breakdown differences in infant death rates between races and look at pages 76 through 89.