In the 241 years since the signing of the Declaration of Independence, 20 total solar eclipses have traced arcs across the United States, astounding professional astronomers and amateur eclipse-chasers alike. Here are a few highlights from the last two-and-a-half centuries of total solar eclipses!
Total Solar Eclipses through U.S. History
June 24, 1778
The total solar eclipse of June 24, 1778, began in the middle of the Pacific Ocean and swept eastward, passing close to Philadelphia. There, it was observed by prominent astronomer David Rittenhouse, whose comments on the eclipse were published in one of the first volumes of the American Philosophical Society’s memoirs.
Thomas Jefferson, who was in Virginia at the time of the eclipse, wrote in a letter to Rittenhouse that “[we] were much disappointed in Virginia generally on the day of the great eclipse, which proved to be cloudy. In [Williamsburg], where it was total, I understand only the beginning was seen.” Jefferson went on to humbly request that Rittenhouse send him a more accurate timepiece—one designed to be “for astronomical purposes only.”
David Rittenhouse. Portrait by Charles Willson Peale.
October 27, 1780
In 1780, Harvard College commissioned the Reverend Samuel Williams, Hollis Professor of Mathematics and Natural Philosophy, to observe the total solar eclipse predicted for October 27, 1780, although the Colonies were still at war with Great Britain. Professor Williams traveled to what is now Penobscot Bay in Maine, where the British naval officer in charge of the area allowed him to land long enough to make his observations. Unfortunately, the maps of the area were so poor that he found himself just outside the path of totality—a misfortune for which he could hardly be blamed!
July 18, 1860
Accurate observations of solar eclipses in the 19th century were sparse until the solar eclipse of July 18, 1860. The Moon’s shadow came in from the Pacific Ocean near where Portland, Oregon, is now located, then moved northeastward across Washington Territory into Canada. This eclipse is remarkable chiefly for the fact that it put an end to the mystery of the red flames seen around the dark disk of the Moon during totality. Early observers believed the flames were caused by “exhalations” or by volcanoes on the Moon. During this eclipse, the flames—called solar prominences—were proven to have their origin on the Sun, not the Moon. They are a result of combustion of the hydrogen that envelopes the entire globe of the Sun.
Solar prominences photographed during the eclipse of May 28, 1900.
August 7, 1869
The total solar eclipse of August 7, 1869, crossed America diagonally from Alaska to North Carolina. The Moon’s shadow entered the United States from Canada, near Simpson, Montana, and then sped southeasterly across the Midwest to the North Carolina coast and out over the Atlantic Ocean. The eclipse path was almost one continuous observatory, lined from beginning to end with astronomical expeditions. Clear skies prevailed on eclipse day.
One of the most intriguing discoveries made was that the spectrum of the solar corona had a mysterious green line in it. This green line was in the same spectral position that was produced by iron in the laboratory, but how could iron be present in the corona? The mystery was not solved until 1941, when the corona was proved to include ionized atoms of iron, as well as nickel, calcium, and the rare gas argon, all at a temperature of a million degrees.
July 29, 1878
On July 29, 1878, over 100 astronomers observed an eclipse along the shadow path from Montana to Texas. During this eclipse, American astronomer James Watson claimed to have seen the much debated planet Vulcan, which was said to exist between Mercury and the Sun. This body, whose existence had never been scientifically established, had been predicted by the French astronomer L.J.J. Leverrier in 1859, but had never been seen. Watson’s announcement that he had observed the object caused a half-century’s fruitless search by leading astronomers. Today, we know there is no planet Vulcan, at least none that could have been seen through Watson’s four-inch telescope.
The theorized position of Vulcan in the solar system. By E. Jones and G.W. Newman, 1846.
Not everyone along the path of totality was an astronomer. A 31-year-old inventor named Thomas A. Edison had brought a pocket-sized device called a “tasimeter” that he claimed could detect a change in temperature of only 0.000001 degree. He announced that he was going to measure the heat of the solar corona, but astronomers were not impressed. Nevertheless, Edison carried out his experiment—and the tasimeter was proven ineffective.
March 7, 1970
During the eclipse of March 7, 1970, the Moon’s shadow, traveling at more than 1500 miles an hour and darkening a 100-mile-wide path of totality, crossed the Gulf of Mexico, entered Florida near Tallahassee, and then sped up the Atlantic coast before heading out over the ocean. Cape Cod narrowly missed seeing totality, but Canada’s Maritime Provinces saw the eclipse as total. The maximum duration of totality was almost four minutes!
February 26, 1979
On February 26, 1979, a total solar eclipse—the last such event to be seen in the United States in the 20th century—was visible from the Pacific Northwest through northern Canada. The total phase began at sunrise in the North Pacific, with the path of totality sweeping through Oregon (where the skies were, unfortunately, completely overcast), Washington, Idaho, and Montana, as well as most of central Canada and Greenland. Maximum duration along the central line was over two minutes.
August 21, 2017
After nearly 40 years, another total solar eclipse will finally be visible in the United States! The path of totality will stretch from Oregon to South Carolina. Check out our Total Solar Eclipse 2017 Guide to learn where and when to watch the eclipse, and click the links below for even more eclipse knowledge!
After the 2017 eclipse, another total solar eclipse will not be visible in the United States until April 9, 2024, when it will pass from southern Texas up through northern New England.
Learn More about Total Solar Eclipses:
- Total Solar Eclipse Folklore, Myths, and Superstitions
- Total Solar Eclipse or Partial Eclipse: Which Will You See?
- How to Safely View the Total Solar Eclipse
- The Best Places to See the 2017 Total Solar Eclipse
Parts of this article originally appeared in The 1979 Old Farmer’s Almanac. The text has been adapted and updated for accuracy.