Navy DDG-51 and DDG-1000 Destroyer Programs: Background and Issues for Congress [Updated October 19, 2021] [open pdf - 1MB]
From the Summary: "The Navy began procuring Arleigh Burke (DDG-51) class destroyers, also known as Aegis destroyers, in FY1985, and a total of 87 have been procured through FY2021, including two in FY2021. From FY1989 through FY2005, DDG-51s were procured in annual quantities of two to five ships per year. Since FY2010, they have been procured in annual quantities of one to three ships per year. DDG-51s are being procured in FY2018-FY2022 under a multiyear procurement (MYP) contract that Congress approved as part of its action on the Navy's FY2018 budget. DDG-51s procured in FY2017 and subsequent years are being built to a design called the Flight III design, which incorporates a new and more capable radar called the SPY-6 radar."
CRS Report for Congress, RL32109
Congressional Research Service: https://crsreports.congress.gov/