If I were still living in New England, it would be the Caps Ridge Trailin New Hampshire.
Where I am now, my current favorite is a section of the Conestoga Trail. However, there are several other very nice hikes not far away, including a very impressive nature hike within the city limits of Philadelphia – Wissahickon Gorge.
Lots of places to go in Portland, for sure. Then there are the nearly unlimited jewels of the Columbia Gorge and the Mt. Hood area.
I love the Congaree Swamp. It’s a bit of a drive, but it’s a beautiful national park (our only one in South Carolina), it’s free free free!, and the trees are magnificent.
The woods behind my house are a good place for a relatively short hike. The Firebug, now 5 years old, frequently drags me on hikes through the thickest, brushiest, most spiderweb-laden parts of the woods - he worries much less about where the paths run than I do, durn his little hide. 
One of the nicest hikes out here on the Oregon coast is theTillamook Head Trail from Seaside over to Indian Beach and Ecola State Park. Beautiful rain forest and ocean views. You can send someone in a car around to Ecola to pick you up if you don’t want to walk back.
While looking at the Google images linked to above for the Tillamook Head Trail I see my car sitting on the beach?!? Oh, it was from another post on another car forum.
Rouge Park in Toronto/Pickering is one of my favourite options. It’s close by, it has a decent variety of terrain, and our favourite trail is just the right length.
Locally I would say the Palisades State Park and the Pipestone National Monument.
Both pretty neat places with extensive hiking trails.