Umatilla County interview questions

I applied to the job, and before a single interview was done, I was requested to fill out a background check form online with my SSN included. I have no doubt this was an official county job, but it is not okay to ask for an SSN that early in the interviewing process. Especially for an online job application, it should be done closer to getting a possible or definite job offer. Why do I have to even explain this? I shouldn't have to explain, to an employer, how identity theft works or what kind of behavior people do to avoid it.