The first emperor of unified China was Qin Shi Huang, who reigned from 221 to 210 BCE. He is known for unifying various warring states into a centralized empire through military conquest and political reform. Qin Shi Huang implemented standardized systems for writing, weights, and measurements, which facilitated trade and communication. His reign also saw the construction of the Great Wall of China to fend off invasions and significant infrastructure projects like the extensive road network. Despite his harsh rule and the use of legalism, he laid the foundations for a unified Chinese identity and significantly impacted subsequent dynasties.