In each county of the state having or which may hereafter have a population of 300,000, the sheriff shall perform all the duties and services now or which may hereafter be required by law to be performed and in addition shall serve all papers, post all notices named by law to be served or posted in behalf of the state or of the county for which elected, including all papers to be served or notices to be posted by the board of county commissioners, the county auditor, or by any other county officer.