When I wanted to learn the tree types I headed west...three miles to Peavy Arboretum. It's nice to walk around and see the labels on the different trees, check the leaves and see the bark. It's open all year so the seasonal changes can be observed. Dogs love it.
The US has many of these and they are usually thorough although some have to stick with regional species due to climate. We are lucky here in Oregon. We get foggy mornings, snow flurries, heavy rain and scorching heat...the afternoons can be a lot different.
Here's a decent list of good arboretums, many constructed by the CCC in the 30's.