Congratulations you have been to all 50! It is time to rest and celebrate!
Time to rest and celebrate and make plans for what is next!!!
After All 50
U.S. Territories
How about visiting all the territories of the USA? Take trips to the 5 inhabited American territories of Puerto Rico, U.S. Virgin Islands, Guam, Mariana Islands, and American Samoa. https://travelgoalgetter.com/travel-blog/youve-been-to-all-50-states-now-what-the-us-territories-are-calling

How about visiting every COUNTY in the USA? The Extra Miler Club is for travellers who count the counties that they visit. Quite an impressive feat! Only 65 travellers are known to have completed this - visiting 3,143 counties, parishes, territories. https://www.extramilerclub.org/
Big City Challenge
How about visiting the biggest cities in the USA? 80 cities with a population of over 250,000. Thank you to 50 stater Gregg Schmidt for inspiring this challenge. https://travelgoalgetter.com/travel-blog/big-city-usa-checklist

How about visiting the highest point in every state? The Highpointers Club is a great resource for those wanting to reach the summit in every state. https://highpointers.org/

How about visiting a national park site in every state? The National Park Travellers Club (NPTC) has tools to keep you motivated to collect park stamps. https://www.parkstamps.org/

How about visiting all 7 continents? A sister club of the All Fifty States Club challenges travellers to visit all 7 continents of the world. North America, South America, Europe, Asia, Africa, Australia, Antarctica. https://travelgoalgetter.com/continent-club.html
Border Crossing Challenge
How entering each state via a different border? All 50 stater Bob Rainville came up with this fun challenge. See states from a different vantage point! https://travelgoalgetter.com/travel-blog/border-crossing-challenge

How about visiting new countries ? A sister club of the All Fifty States Club challenges travellers to count up the countries they visit. Bronze Level membership begins at 15 countries visited, Silver for 30 countries, Gold for 50 countries, and Platinum for 100 countries. https://travelgoalgetter.com/travelers-country-club.html

How about visiting 100 countries or more? The Traveller's Century Club sets the bar high as you can only join once you have visited 100 countries and motivates travellers to visit every country in the world. https://travelerscenturyclub.org/about

How about visiting our neighbors to the North and travel to all 13 Canadian provinces and territories? You may have gone to 2 or 3 already if you drove to Alaska as part of your 50 state journey!
Visit all 50 states again with a new spin! Visit a factory in every state, attend a baseball game in every state, visit all the capitols.
Travel Route 66, hike the Appalachian Trail, follow the Natchez Trace Parkway, ride the Mississippi River.