Elevation Graph

I found this site which makes elevation graphs of your commute:
Google Maps elevation for a route

Pan around by clicking and dragging the map. Use the zoom in/out with your mouse wheel to move large distances. It will zoom in to where your mouse is pointed (e.g zoom out to see the whole world and the hover your mouse over your area and zoom in using the mouse wheel).

It defaults to kilometers/meters for distance/altitude. Click the Options link to select miles if you prefer miles.
Just click on the map to create a navigation point. You're limited to 25 points so try to keep it to intersections and don't include obvious necessary turns. It seems to be aware of which lane you click on so if you click on the wrong side of the road, it will make a u-turn to get to that point (adds miles) so zoom in on the freeway to make sure you're clicking the right lane.

When you're done, click the "Get Elevation" button. It will generate a image similar to below.
Examine the route to make sure nothing weird is going on. I typically get on at a direct HOV access ramp but the map here doesn't know that so it added about a 3 miles loop to connect two points which should have been direct. In that case, I just deleted a few points to make the route a little more direct (hover over the point to see it's number and delete it from the list). Use a picture grabber to get the graph. Windows 10 has a snipping tool to select a screen grab (Windows button->Type Snipping Tool).

Once it's generated, hovering your mouse over the elevation chart will show where it corresponds to on the map with a little moving dot. I used that to delineate highway from city driving and used MS Paint to add vertical lines. I then used Paint's fill function to change the color to show my freeway portion (draw the lines first so it will only fill in that section).

On my graph, grey is city and blue is freeway. Here's my commute of 43 miles (900ft to sea level):