Looking for a record in Illinois? Record keeping, that is birth and death certificates, was encouraged but not mandated until 1916. For a list of the earliest records in Illinois courthouse go here:

http://ilgenweb.net/countybmd.html

Note that "earliest" and "complete" are nowhere near the same. I note that in rural counties if they were born or died in the summer there is more likely to be a record prior to 1916.