The modern trumpet is basically a pipe (like a flute or shawm), while ancient trumpets were horns. Distinguishing between these historic variations depends on which features are highlighted. One possible distinction is to regard horns literally as horns made of animal horns, while instruments that are made to simulate animal horns, but constructed of metal, are regarded as trumpets. Both horns and trumpets are played with vibrating lips, which result in the Bernoulli effect. The oldest trumpets date back to 1500 BCE and perhaps even earlier. There were trumpets (made of bronze and silver metals) found Tutankhamun's grave in Egypt.
Modern trumpets have valves to offer more control over changing the length of the pipe. To reduce the length of the instrument, the body pipe is bent twice, making it much easier to handle. The box valve was invented in the early 1800s and revolutionized trumpet playing. Having keys to press to change tone extended the tonal scope of trumpets.
Early 1800s.
Source: http://www.miayf.org/brasswind/trumpet/
http://www.beginband.com/sndclips.shtml