When you look through your oven door to check on something baking in there, you can thank a Cincinnati, Ohio man named Ernst H. Huenefeld. He invented the glass oven door in 1909.
The door was fitted with special metal frames that let the glass expand and contract without breaking, which was a very good thing. Huenefeld's company made Boss brand ovens, which allowed you to be the boss of your cakes and casseroles in a way you simply hadn't been before. I don't know that that's the reason they called the company Boss, but it would work, wouldn't it? You can see a 1920s Boss oven that's for sale over here.
Before I saw this ad I never really thought about glass oven doors. My aunt had a wonderful old white enamel oven range without a glass panel in the door. I think it dated from the 1930s, when her house was built. She never seemed to have any problem cooking in it. It had all sorts of built in shelves and doors and I have always wanted a range just like hers.
Having said that, I also depend a lot on checking stuff through that little window, don't you? Although what usually happens with me is that I put something in, go downstairs to my office to write, and then suddenly remember oh no stuff is in the oven! and go running upstairs to check on it. That's one advantage of writer's block, I suppose - your mind wanders around. Ideally it wanders back to what's in the oven and how you need to stop trying to write and check whether you've carbonized the muffins.