Extremities of the Earth: The Longest River (Part 1)

The Amazon or the Nile? The debate over which deserves the title of longest river is centuries old. Determining the world’s longest river is not a simple matter of using a measuring tape to find the distance! In this new post in our Extremities of the Earth series, we will explore these two mighty waterways that have each been called the world’s longest river.

Today, the most common answer to which is the world’s longest river is the Nile River in northeast Africa. However, it wasn’t until the mid-19th century that that source of the Nile was discovered. Before then, the Amazon River in South America was considered the world’s longest river, as can be seen in the chart engraved by Thomas Starling below. Published in 1846 in an atlas titled Maps of Useful Knowledge, all the principal rivers of the earth are shown. The center of the map shows the name and mouth of each river with the river then drawn outward towards their sources on the outer edge of the page. The index lists the Amazon as 3,200 miles and the Nile as 2,750 miles, both of which can be seen in the detail below.

Starting in the Andes Mountains of Peru, the Amazon River flows west to east across nearly the entire South American continent and has been sustaining life for millennia. The earliest evidence of human habitation near the Amazon comes from shell mounds and earth platforms found along the river, with one recently found archaeological site dating to 1000 BC. In March 1500, Spanish conquistador Vicente Yáñez Pinzón was the first documented European to sail up the Amazon River. Several accounts from early Spanish explorers tell of great cities built along the mighty waterway. One such account was from Francisco de Orellana, who in 1540, completed the first known navigation of the entire length of the Amazon River. It is de Orellana who gave the name “Amazon” to the river after his expedition was attacked by a group of natives led by women, reminding him of the ancient Greek myth of the Amazon women warriors.

About 150 years later, in 1689, a Czech Jesuit missionary named Samuel Fritz made the journey down the Amazon River. His are the first known maps to be drawn by someone who had navigated the Amazon River from one end to the other. Fritz’s map, a facsimile of which can be seen below, is remarkably accurate in showing the contours of the river and the South American continent. A version of Frtiz’s 1691 map was first published in Quito in 1707, and the map became widely published around Europe. About the map, Fritz wrote in his journal:

For better understanding and general information concerning this great river Marañón or Amazons, I have made this geographical map with no little toil and exertion, having navigated it in the greater part of its course as far as it is navigable.

Throughout the 17th, 18th, and 19th centuries, the Amazon River continued to be explored. The actual course of the river only runs through 2 countries, Peru and Brazil, but the Amazon basin covers a much larger area and is the largest in the world. Including over 1,100 tributaries that run into the river, the basin covers 8 countries and about 40% of the whole continent. While debate exists about the true length of the river, there is no question that the Amazon contains the greatest volume of water. The Amazon is responsible for about 20% of the Earth’s fresh water entering the ocean! During the rainy season, the river can grow up to 30 miles wide, which means there are no bridges crossing the Amazon. The German map below, made in 1914 by Ludwig Koegel, highlights the greater Amazon basin area which has expanded even more today.

It is difficult to determine the exact length of a river due to many factors, such as determining the source of a river, the identification or the definition of the mouth, the scale of measurement, the curves of the shore, and more.

For many years, the headwaters of the Apurímac River on Nevado Mismi, a mountain in the Andes Mountains of Peru, had been considered the source of the Amazon, making the river about 4,130 miles (6,650 km) long. A study done in 2014 by Brazilian scientists calculated a new length for both the Amazon and the Nile, concluding that the Amazon was 4,345 miles (6,992 km), or 139 miles longer than the Nile. This claim has been disputed by other geographers. This leaves the title of longest river open to continued debate, more of which will be discussed in Part 2 of this post about the competing waterway, the Nile River in northeast Africa!