Pre-Columbian era
The earliest known civilization is the Olmec. This civilization established the cultural blueprint by which all succeeding indigenous civilizations would follow in Mexico. Pre-Olmec civilization began with the production of pottery in abundance, around 2300 BCE in the Grijalva River delta. Between 1600 and 1500 BCE, the Olmec civilization had begun, with the consolidation of power at their capital, a site today known as San Lorenzo Tenochtitlán near the coast in southeast Veracruz. The Olmec influence extended across Mexico, into Central America, and along the Gulf of Mexico. They transformed many peoples' thinking toward a new way of government, pyramid-temples, writing, astronomy, art, mathematics, economics, and religion. Their achievements paved the way for the Maya civilization and the civilizations in central Mexico.
Harappa
The Harappan Civilization has its earliest roots in cultures such as that of Mehrgarh, approximately 6000 BC. The two greatest cities, Mohenjo-daro and Harappa, emerged circa 2600 BC along the Indus River valley in Punjab and Sindh. The civilization, with a possible writing system, urban centers, and diversified social and economic system, was rediscovered in the 1920s also after excavations at Mohenjo-daro in Sindh near Larkana, and Harappa, in west Punjab south of Lahore. A number of other sites stretching from the Himalayan foothills in east Punjab, India in the north, to Gujarat in the south and east, and to Pakistani Balochistan in the west have also been discovered and studied. Although the archaeological site at Harappa was damaged in 1857 when engineers constructing the Lahore-Multan railroad (as part of the Sind and Punjab Railway), used brick from the Harappa ruins for track ballast, an abundance of artifacts have nevertheless been found. The bricks discovered were made of red sand, clay, stones and were baked at very high temperature. As early as 1826 Harappa, located in west Punjab, attracted the attention of a British officer in India, who gets credit for preliminary excavations in Harappa.