1987- EPA recognizes the Delaware Estuary as an estuary of significance
1988 - The Delaware Estuary becomes part of the EPA's National Estuary Program
1990 - Estuary News produced by the Pennsylvania Environmental Council
1997 - DNREC assists PDE in establishing its first office at Bellevue State PArk in Wilmington, Delaware
1996 - PDE officially incorporated as a non-profit organization
1996 - The Delaware Estuary Program publishes the first Comprehensive Conservation Management Plan
1997 - First PDE logo created by local illustrator Frank McShane
1999 - PDE holds the first Experience the Estuary Celebration
1998 - Thirty Educators Attend the First Delaware Estuary Teacher’s Institute
2000- PDE office moves to 9th and Orange streets in downtown Wilmington, Delaware
2004 - PDE becomes the host of the Delaware Estuary Program
2002- PDE holds the first Pennsylvania Coast Day (now the Delaware River Festival) at Fairmount Water Works in Philadelphia
2005 - the Delaware Bay Oyster Restoration Project and campaign launched, with 280,000 bushels of oyster shell planted the first year
2005 PDE office moves to the Riverfront in Wilmington, Delaware
2005- First Delaware Estuary Science & Environmental Summit takes place, brining together 248 people
2007 First freshwater mussel hatchery lab established in partnership with Cheyney University
2018 - Representatives from partner agencies sign a memorandum of understanding for the Aquatic Research and
Restoration Center ( ARRC), paving the way for a future large-scale mussel hatchery
2021 - PDE celebrates its 25th anniversary