Question: When was the American explorer which was accompanied by Lake Sacajawea during their exploration of the American West born?

Context paragraphs:
John C. Frémont botanical nomenclature eponyms: John C. Frémont (January 21, 1813July 13, 1890) was a 19th Century American explorer of the West during the 1840s and 1850s, popularly known as the "Pathfinder".  His first two published expeditions launched a mass emigration into the American West producing maps and reliable reports for settlers to read and follow.  In the process of botanical nomenclature ("plant naming"), Frémont received many eponyms in his honor and for his work as a botanist.  His genus name eponym is "Fremontodendron", while his species eponym is "fremontii".  Frémont went on a total of five expeditions; the first three were federally sponsored while Frémont served as a military officer.  On these expeditions he was guided by mountain man Kit Carson.  Frémont's fourth and fifth expeditions were privately sponsored.  Although Frémont's life was controversial, he was considered an American hero.  Frémont's published works, co-authored by his wife Jessie, could either be read scientifically or as adventure stories, capturing the public's attention, and creating enthusiasm for Westward migration.

Lake Ellsworth (Antarctica): Lake Ellsworth is a subglacial lake located in West Antarctica under approximately 3.4 km of ice.  It is approximately 10 km long and is estimated to be 150 m in depth.  The lake is named after the American explorer Lincoln Ellsworth.

John C. Frémont: John Charles Frémont or Fremont (January 21, 1813July 13, 1890) was an American explorer, politician, and soldier who, in 1856, became the first candidate of the anti-slavery Republican Party for the office of President of the United States.  During the 1840s, when he led four expeditions into the American West, that era's penny press and admiring historians accorded Frémont the sobriquet "The Pathfinder".

Antoine Auguelle: Antoine Auguelle Picard du Gay (alternative spelling "Augelle", also referred to as Anthony Auguel) was a 17th-century French explorer.  Born at Amiens in Picardy, Auguelle along with Michel Aco accompanied Father Louis Hennepin during his exploration of the Upper Mississippi River.  Setting out from Fort Crevecoeur in present-day Illinois on none }} , the trio were briefly captured by a band of Santee Sioux on none }} near Mille Lacs Lake in present-day Minnesota.  During their captivity, they were escorted to such memorable Minnesotan landmarks such as Saint Anthony Falls, Lake Pepin, and Kaposia, in the process becoming the first Europeans to do so.  They were finally released at the end of September 1680 at the insistence of explorer Daniel Greysolon, Sieur du Lhut.

Windust Caves Archaeological District: The Windust Caves are a series of nine caves that have been eroded into the side of a basalt cliff on the north side of the lower Snake River.  The caves were excavated from 1959 until 1961 by a crew led by Harvey S. Rice.  Some of the caves had been disturbed, though also somewhat preserved from looting by collectors, by rock falling off the roofs of the caves during construction of the Northern Pacific Railway.  Other caves were damaged by collectors.  In 1961, upon completion of the Ice Harbor Lock and Dam, the caves were flooded by the reservoir known as Lake Sacajawea.

Meriwether Lewis: Meriwether Lewis (August 18, 1774 – October 11, 1809) was an American explorer, soldier, politician, and public administrator, best known for his role as the leader of the Lewis and Clark Expedition, also known as the Corps of Discovery, with William Clark.

Lake Sacajawea: Lake Sacajawea is formed by the Ice Harbor Dam on the Snake River.  It stretches from there upstream to the Lower Monumental Dam.  It is named for Sacajawea, a Shoshone woman who accompanied Meriwether Lewis and William Clark during their exploration of the American West.

Frederick Cook: Frederick Albert Cook (June 10, 1865August 5, 1940) was an American explorer, physician, and ethnographer, noted for his claim of having reached the North Pole on April 21, 1908.  This was a year before April 6, 1909, the date claimed by the American explorer Robert Peary, and the accounts were disputed for several years.  His expedition did discover Meighen Island, the only discovery of an island in the American Arctic by a United States expedition.

America's Western Frontiers: America's Western Frontiers: The Exploration and Settlement of the Trans-Mississippi West (released in the United Kingdom as The American West) is a book which chronicles the history of the American West from the Pre-Columbian era through the mid-twentieth century.  It was written by John A. Hawgood, a professor of history at the University of Birmingham in England, whose speciality was the history of the American west.  The book was first published by Alfred A. Knopf in 1967.

SS Meriwether Lewis: The SS "Meriwether Lewis" (Hull Number 170) was a Liberty ship built in the United States during World War II.  She was named after Meriwether Lewis, an American explorer who, along with William Clark, led the Corps of Discovery which explored the American West.

Supporting paragraphs: Lake Sacajawea Meriwether Lewis
Answer: August 18, 1774