Last Updated on 22 September 2023
| August | Events |
| 1 | 1916 – Haleakala National Park, HI created 1916 – Hawaii Volcanoes National Park, HI created 1974 – Constitution Gardens, DC created |
| 2 | 1876 – Washington Monument, DC accepted 1937 – Capitol Reef National Park, UT created 1956 – Virgin Islands National Park, VI created |
| 3 | 1918 – Casa Grande named a National Monument 1938 – Hopewell Furnace National Historic Site, PA created 1950 – Greenbelt Park, MD created |
| 4 | 1920 – Great American Outdoors Act signed into law |
| 5 | |
| 6 | |
| 7 | 1961 – Cape Cod National Seashore, MA created |
| 8 | |
| 9 | 1916 – Capulin Volcano National Monument, NM created |
| 10 | 1933 – Fort Donelson National Battlefield, TN created 1933 – Kings Mountain National Military Park, SC created 1933 – National Capital Parks, DC created 1933 – Tupelo National Battlefield, MS created 1936 – Joshua Tree National Park, CA created |
| 11 | |
| 12 | 1940 – Fort Washington Park, MD created 1946 – Castle Clinton National Monument, NY created 1965 – Herbert Hoover National Historic Site, IA created |
| 13 | |
| 14 | 1958 – General Grant National Memorial, NY created |
| 15 | 1978 – Chattahoochee National Recreation Area, GA created 1978 – War in the Pacific National Historical Park, GU created |
| 16 | |
| 17 | 1937 – Cape Hatteras National Seashore, NC created 1972 – Pu’ukohola Heiau National Historic Site, HI created |
| 18 | 1971 – Lincoln Home National Historic Site, IL created |
| 19 | 1890 – Chickamauga and Chattanooga National Military Park, GA & TN created 1976 – Ninety Six National Historic Site, SC created |
| 20 | 1969 – Florissant Fossil Beds National Monument, CO created |
| 21 | 1935 – Fort Stanwix National Monument, NY created 1965 – Alibates Flint Quarries National Monument, TX created |
| 22 | 1933 – Cedar Breaks National Monument, UT created |
| 23 | |
| 24 | 2016 – Katahdin Woods and Waters National Monument, ME created |
| 25 | 1916 – National Park Service founded 1937 – Pipestone National Monument, MN created 1972 – Grant-Kohrs Ranch National Historic Site, MT created 1972 – John D. Rockefeller, Jr., Memorial Parkway, WY created |
| 26 | 1992 – Marsh-Billings National Historical Park, VT created |
| 27 | 1964 – Ozark National Scenic Riverways, MO created |
| 28 | 1965 – Hubbell Trading Post National Historic Site, AZ created 2011 – Martin Luther King, Jr. Memorial, DC created |
| 29 | 1935 – Andrew Johnson National Historic Site, TN created |
| 30 | 1890 – Antietam National Battlefield, MD created 1964 – Fort Bowie National Historic Site, AZ created |
| 31 | 1964 – Allegheny Portage Railroad National Historic Site, PA created 1964 – Fort Larned National Historic Site, KS created 1964 – John Muir National Historic Site, California 1964 – Johnstown Flood National Memorial, PA created 1964 – Saint-Gaudens National Historic Site, NH created |
