Although modern sculpture and architecture are reckoned to have emerged at the end of the nineteenth century, the beginnings of modern painting can be located earlier. The date perhaps most commonly identified as marking the birth of modern art is 1863, the year that Édouard Manet exhibited his painting Le déjeuner sur l 'herbe in the Salon des Refusés in Paris. Earlier dates have also been attributed to 1855, the year Gustave Courbet exhibited The Artist 's Studio and 1784. the year Jacques-Louis David completed his painting The Oath of the Horatii.
Which one is right? Well, none of them are "wrong". (Here, it was simply a case of "1880" working out well, for me, in terms of organization.) For simplicity 's sake, let 's just say that Modern Art began in the 19th-century, and ran through a whole slew of "-isms" up until the end of the 1960 's. Regardless of chosen starting date, the crucial factor is that Modern Art means: "The point at which artists (1) felt free to trust their inner visions, (2) express those visions in their work, (3) use Real Life (social issues and images from modern life) as a source of subject matter and (4) experiment and innovate as often as possible.
The single most important thing one need remember about Modern Art is that it is entirely different from Contemporary Art. Modern Art began around the time
Cited: 1) Hughes, Robert The Shock of the New (1991), New York: McGraw-Hill