Illinois data from the 2010 Census is available by navigating to the state here. To look at data for specific counties, municipalities, or even census tracts and blocks, you will want to look at "areas within," select Counties, and continue to navigate until you find the geographical unit you are looking for.
For instance, to get to the main campus of Knox College (Tract 8, Block 2022), you would want to select Illinois-Areas Within-Counties-Knox County-Areas Within-Census Tracts-Tract 8-Areas Within-Block 2022. Notice that this block had a population of 651 in 2010, all but 2 of whom were 24 years of age or younger! The same is true for Tract 8, Block 2019, which also includes only on-campus housing.
To figure out which census blocks and tracts you need to examine, look here (local data for other states is here). Within the state listings, go to the appropriate county and select the city or township that encompasses the block you are looking for. For example, you can look at the census blocks and tracts for Galesburg City in Knox County. The most useful map for the city of Galesburg is A01.
Note: 2010 Census did not contain detailed demographic information such as income. For those statistics, you will have to use data from the American Community Survey, also available through American FactFinder.