Most historians cite the modern world starting with the French Revolution overturning the entrenched systems of aristocracy, religion, and so forth. Art historians often cite Manet's Luncheon on the Grass, from 1863, as the beginning of modern art.
Now, you may have a few special pieces of furniture that have been passed down to you. You easily spot them in a room since they look so much bulkier or ornamental from everything else. The idea of sleek, functional, straight-line furniture and design does not belong to Le Corbusier alone. But he is a great representative of the movement.
Consider another modern architect, Frank Lloyd Wright. Wright's buildings stick out due to their bold designs, like the Guggenheim in New York. Le Corbusier instead went for the International Style: the modern skyscraper owes a great deal to Corbusier's simple functionalism.
Like Wright he played with concrete, and unlike Wright, his concrete buildings gained acceptance and showed that by exposing the basics of a structure you need not sacrifice its beauty. From helping design the UN headquarters to projects at Harvard, Tokyo, Baghdad, and his adopted France, along with many others, Corbusier gave the international style a longer permanency on the landscape than other movements like Art Deco. He also stuck with it much longer than others like Gropius.
Eventually the International style lost the beauty and was replaced with the soulless monuments we see around us. Consider the UN headquarters – it would be inspiring if it was the only one that looked like it. But as tens of thousands appear like it across the world the luster wanes.
Not surprisingly, then, his work as a city planner left behind architecturally marvelous, but rather harsh cities. As modern architecture goes, even as it is now finally starting to distance itself from the unyielding utilitarian functionalism, Le Corbusier can take much credit for a century of buildings.