when was the rank of senior and master chief petty officer established
Master chief petty officer Prior to 1958, chief petty officer was the highest enlisted rate in both the U.S. Navy and U.S. Coast Guard. This changed on 20 May 1958 with the passage of Public Law 85-422, the Military Pay Act of 1958, which established two new enlisted pay grades of E-8 and E-9 in all five branches of the U.S. Armed Forces. In the U.S. Navy and U.S. Coast Guard, the new E-8 pay grade was titled Senior Chief Petty Officer and the new E-9 pay grade as Master Chief Petty Officer, with the first selectees promoting to their respective grades in 1959 and 1960.[2]