April 30, 1803
The United States finalizes the Louisiana Purchase from France, adding the land from the Mississippi River to the Rocky Mountains to its territory.

October 1803
Meriwether Lewis, of the legendary duo Lewis and Clark, collects bone specimens at Big Bone Lick, in what is now Boone County, Kentucky.

July 25, 1806
Near the Yellowstone River, William Clark notes an exposed rib bone in the Hell Creek Formation. Paleontologists claim this is the first documented dinosaur fossil discovery on the North American continent.

September 6, 1807
Clark spends three weeks at Big Bone Lick in America's first organized vertebra paleontology expedition. He uncovers a significant cache of bones of creatures presumably drawn to the area by a salt lick.

1822
Henri Marie Ducrotay de Blanville, editor of the French Journal de Phisique, coins the term "paleontology" to refer to the study of ancient animals by using fossils.

April 1824
Congress authorizes the Army Corps of Engineers to complete surveys on roads and canals. This marks the first federally funded survey of the U.S., geographically or geologically.

October 29, 1831
Othniel Charles Marsh is born in Lockport, New York.

1837
Swedish biologist Louis Agassiz proposes his Ice Age theory to a hostile audience. His publication Recherches sur les Poissons Fossiles ("Research on Fossil Fish,") released in five volumes from 1833-43, described over 1,700 species of ancient fish. In 1847, Agassiz will become a professor at Harvard University.

1840
English paleontologist Richard Owen coins the term "dinosaur," which means "terrible reptile."

July 28, 1840
Edward Cope is born in Philadelphia, Pennsylvania.

August 10, 1846
The Smithsonian Institution is established after the nephew of British scientist James Smithson dies without an heir. As stipulated by Smithson's will, part of his sizable estate is left "to the United States of America, to found at Washington, under the name of the Smithsonian Institution, an establishment for the increase and diffusion of knowledge among men." The Institution will eventually shelter United States collections of cultural and natural historical artifacts.

1852
Dr. Joseph Leidy publishes 13 paleontological papers in one year.

1858
Leidy makes Hadrosaurus the first North American dinosaur to be described from a nearly-complete skeleton. In collaboration with William Foulke, the skeleton is retrieved from a New Jersey mineral pit in 1858 and will be fully assembled for display at the Philadelphia Academy of Natural Sciences ten years later.

November 24, 1859
English naturalist Charles Darwin publishes On the Origin of Species, introducing the concept of natural selection to the theory of evolution.

May 15, 1862
Congress establishes the Department of Agriculture to provide "useful information on subjects connected with agriculture in the most general and comprehensive sense of that word."

Winter 1863
O.C. Marsh and Edward Cope meet for the first time in Berlin, while Marsh is studying at the University of Berlin and Cope is touring Europe. Their amicable relationship will turn famously antagonistic in coming years.

March 3, 1863
Abraham Lincoln establishes the National Academy of Sciences to "investigate, examine, experiment, and report upon any subject of science or art" when requested by the government.

1866
In his article "Discovery of a Gigantic Dinosaur in the Cretaceous of New Jersey," Edward Cope describes an incomplete skeleton of a dinosaur and names it Laelaps aquilunguis, meaning "eagle-clawed terrible leaper." In 1877, Marsh will rename the creature Dryptosaurus, after discovering that the name laelaps had already been used to designate a breed of mite.

This same year, Marsh becomes chair of paleontology at Yale.

1867
For the first time, Congress authorizes geological explorations in the American West. Over the next decade, the King survey, the Hayden survey, the Powell survey and the Wheeler surveys will make the first federally funded forays into geological observation.

August 1868
Marsh visits the American West for the first time on the Union Pacific Railroad during an excursion for the annual meeting of the American Association for the Advancement of Sciences.

1869
Cope reconstructs a plesiosaur he calls Elasmosaurus platyrus. Upon seeing it, Marsh believes Cope has placed the skull on the wrong end of the skeleton; Marsh shows the bones to Leidy who confirms the error, and Cope is humiliated. Cope frantically attempts to recall all printed publications of his findings and publishes a corrected version. Marsh would later write "His wounded vanity received a shock from which it has never recovered, and he has since been my bitter enemy."

May 10, 1869
The Transcontinental Railroad is completed. Trains allow Americans easier access to the West, setting the foundation for the fossil-searching expeditions that will follow.

Fall 1870
In Kansas, Marsh uncovers the first North American pterosaur during his premiere fossil-hunting expedition to the West. Initially led by Buffalo Bill Cody, Marsh is accompanied by a cadre of Yale undergraduates.

October 1871
An attending Yale student publishes an article in Harper's Monthly describing his six months on a geological expedition with Marsh. The account includes run-ins with grizzly bears, Indians, and a day spent with Buffalo Bill Cody.

July 1872
At Fort Bridger, Wyoming, Leidy finds the bones of a creature with elephant-like legs, tusks, and other bony knobs on its skull. He names the fragments Uintatherium robustum.

Also working in Fort Bridger both Marsh and Cope find similar fossils. Rushing to describe and identify their findings, the scientists end up giving the creature three different names.

This is the year that Marsh uncovers examples of toothed birds in Kansas which seem to contribute to Charles Darwin's theory of evolution. Marsh's wide collection of prehistoric horse fossils also provides useful evidence for the theory.

June 1873
Cope and Marsh make their feud public with a series of criticisms, defenses, and rebuttals in The Naturalist.

1875
Marsh publishes "Odontornithes, or Birds with Teeth."

Summer 1876
Cope heads to Montana on a fossil-hunting expedition, where he finds fossils of a creature he names Monoclonius.

August 1876
English biologist Thomas Huxley visits Marsh at Yale and is impressed with his collection of horse fossils, documenting the animal's evolution on the North American continent.

Spring 1877
Amateur painter Arthur Lakes discovers large bones in Morrison, Colorado and sends some to both Cope and Marsh. The two rush to the site and hear of an even greater find in Como Bluff, Wyoming. Frantically, they each try to gather more samples than the other.

This year, Marsh will name the Stegosaurusfrom bones found near Morrison, Colorado as well as the Apatosaurus ajax. Two years later, he will name another specimen Brontosaurus excelsus, believing it to belong to another genus. However, it is later determined that the two creatures belong to the same genus, and the term Brontosaurus is dropped from formal usage.

March 3, 1879
Congress consolidates the four largest surveys in the West into the United States Geological Survey with the mission to initiate an encompassing national survey.

March 1881
John Wesley Powell takes over the U.S. Geological Survey and names Marsh Chief Paleontologist.

1882
Quarrying operations at Nevada State Prison reveal fossilized animal tracks initially believed by prisoners to belong to pre-Adamite humans. Edward Cope supports the theory; Marsh and others determine that the two million-year-old tracks belong to a giant ground sloth from the late Pliocene age.

1883
Marsh becomes president of the National Academy of Sciences.

1884
Cope publishes over 70 papers throughout the year, describing his findings from his travels in the West.

1887
The first ever Triceratops fossil is found near Denver, Colorado and sent to O.C. Marsh.

Fall, 1889
Cope takes a teaching position as Professor of Zoology and Comparative Anatomy at the University of Pennsylvania.

December 16, 1889
At Marsh's behest, John Wesley Powell announces an audit of Cope's holdings; Cope will be required to return items retrieved using federal funds to the government. The suggestion infuriated Cope, who had spent much of his own money on his expeditions.

January 12, 1890
The feud between O.C. Marsh and Edward Cope hits a crescendo with personal attacks printed in the national newspaper The New York Herald. The series of disparaging articles accusing each other of plagiarism, incompetence and fraud lasts two weeks.

Summer 1890
In response to the smear campaign in the papers, Congress cuts over a fourth of the Geological Survey budget, firing Marsh and his entire Department of Paleontology.

The Smithsonian claims all fossils collected under US Geological Survey funds, and Marsh is eventually forced to hand over more than 80 tons of fossils from his coveted collection.

April 12, 1897
Edward Cope dies.

March 19, 1899
O.C. Marsh dies.