Applications needs my current Monthly Salary?

Is it normal for a job to ask you for your monthly salary for each and every job you've had? This feels weird and I suspect it will be used to undercut me on pay if I get the job. I'm applying to work for the county and I'm using governmentjobs.com

usa jobs
usa jobs resume
usa hotel jobs
usajobs
usa jobs federal government
usa job in ksa
usa jobs
usa jobs login
usa jobs gov
usajobs.gov
www.usajobs.gov
usajobs.com
usajobs
usajobs.gov official