Final answer:
The Arab-Muslim Empire, established during the 7th century, is known as the largest empire, expanding 300 miles from east to west, even surpassing the Roman Empire under Trajan and later the massive Mongol Empire under Chinggis Khan.
Step-by-step explanation:
The largest empire in history, spanning 300 miles from east to west, refers to the Arab-Muslim Caliphate that emerged in the 7th century. The Arab-Muslim Empire was even larger than the Roman Empire at its peak under Emperor Trajan in 117 CE, which was previously considered one of the greatest in terms of territorial expanse. Another contender for this title was the Mongol Empire, which was the largest contiguous land empire in history and was created swiftly by Chinggis Khan and his descendants in the 13th century.
There are other empires that are notable for their size and impact, such as the Akkadian, Sumerian, Persian, and Ming empires. Each of these civilizations had periods of significant expansion, for example, under Sargon of Akkad or Cyrus the Great. However, when it comes to sheer size and the area covered, the aforementioned Arab-Muslim and Mongol empires stand out as the largest in history.