When was the first automobile built?
we dont know
Depends on definition what an automobile is. The first self-propelled vehicle with an internal-combustion engine (as definition is generally) was built by Carl Benz in Germany in 1889.
The first steam-powered land vehicle was the "Fardier" by Nicolas-Joseph Cugnot, introduced in 1769. It had a 2-cylinder steam engine and was intended for trailing guns for the French artillery but failed that duty. Nevertheless, it was driveable. It still exists in France.