Question: What was the original name of the dam that serves as the northern boundary of the Topock Marsh?
Context: Illinois is in the midwestern United States.  Surrounding states are Wisconsin to the north, Iowa and Missouri to the west, Kentucky to the south, and Indiana to the east.  Illinois also borders Michigan, but only via a northeastern water boundary in Lake Michigan.  Nearly the entire western boundary is the Mississippi River, except for a few areas where the river has changed course.  Illinois' southeastern and southern boundary is along the Wabash River and the Ohio River.  Whereas, its northern boundary and much of its eastern boundary are straight survey (longitudinal and latitudinal) lines.  Illinois has a maximum north-south distance of 390 miles (630 km) and 210 miles (340 km) east-west.  Its total area is 57918 sqmi . Catfish Paradise is an unincorporated community in Mohave County, Arizona, in the United States.  It is located at the southern end of the Topock Marsh along the Colorado River. Fermoy (Irish: "Mainistir Fhear Maí" ; formerly also Armoy) is a barony in County Cork in Ireland.  It is bordered by the baronies of Orrery and Kilmore to the north-west; Duhallow to the west; Barretts to the south-west; Barrymore to the south; Condons and Clangibbon to the east; and Coshlea, County Limerick to the north.  It is bounded to the south by the Nagle Mountains and the valley of the Munster Blackwater.  The Ballyhoura Mountains mark the northern boundary.  A tributary of the Blacckwater, the Awbeg has two branches in its upper stretches; one branch forms the northern boundary while the other near Buttevant, forms the western limit.  To the east, lies another Blackwater tributary, the Funcheon.  Anomalously, the namesake town of Fermoy is actually in the barony of Condons and Clangibbon.  The town with the greatest population in the barony is Mallow (8578 people per Census of 2006). Little Walker Caldera is a depression in the eastern Sierra Nevada that is adjacent to the Sweetwater Mountains.  The caldera is very large, measuring about 18 km in diameter.  The Little Walker Caldera is named for the Little Walker River; it is the river that is little, not the caldera.  U.S. Route 395 in California crosses the Northern boundary of the caldera, just west of the Devil's Gate Pass.  California State Route 108 follows more of the northern boundary of the caldera. Potchefstroom Dam is dam on the Mooi River, on the northern boundary of Potchefstroom, North-West, South Africa.  It was established in 1950. Holgate is a suburb and unitary authority ward in the City of York.  It is bounded by the River Ouse from Scarborough Bridge to Ouse Acres on its northern boundary.  Its western boundary is formed by one side of Carr Lane and Ouse Acres to the junction of York Road/Acomb Road, which forms part of the southern boundary.  The remainder of the southern boundary follows Moorgate and Holgate Beck to the East Coast Main Line railway which completes the eastern boundary as far as the River Ouse/Scarborough Bridge. Ridgefield Township was a township that existed in Bergen County, New Jersey.  The township was created in 1871, when Hackensack Township was trisected to form Palisades Township in the northernmost third, Englewood Township in the central strip and Ridgefield Township encompassing the southernmost portion, stretching from the Hudson River on the east to the Hackensack River, with Hudson County to the south.  Much of the area had been during the colonial area known as the English Neighborhood.  As described in the 1882 book, "History of Bergen and Passaic counties, New Jersey," "Ridgefield is the first township in Bergen County which the traveler enters in passing up the Palisades.  His first impressions are much like those of old Hendrick Hudson in speaking of a wider extent of country: "A very good land to fall in with, and a pleasant land to see."  The valley of the Hackensack invited early settlers in the seventeenth century, and the valley of the Overpeck Creek, a navigable arm of the Hackensack, also attracted settlers quite as early in this direction.  Sloops and schooners can pass up this creek nearly to the northern boundary of the township.  Ridgefield is bounded on the north by Englewood, on the east by the Hudson, on the south by Hudson County, and on the west by the Hackensack River.  The southern boundary is less than two miles in extent, and the northern less than four, and the length of the township from north to south does not exceed four miles.  Bellman's Creek, forming part of the southern boundary, the Hackensack, the Overpeck, the Hudson, with more than a dozen other smaller streams and rivulets, bountifully supply the whole township with water.  From the western border of the Palisades the land descends to the Overpeck, forming a most beautiful valley, with the land again rising to a high ridge midway between the Overpeck and the Hackensack.  From this long ridge, extending far to the north beyond this township, it took its name of Ridgefield. <br><br>The New York, Susquehanna and Western, formerly the Midland Railroad, the Jersey City and Albany Railroad, and the Northern Railway of New Jersey—all running northward through the township— afford ample railroad accommodations.  The Susquehanna enters the township at Bellman's Creek, and the Northern at about one hundred feet south of the creek, and at a point north and east of the Susquehanna.  The Albany road in this locality is not yet constructed, diverging at present from the track of the Susquehanna between Little Ferry and Bogota stations.  It has, however, an independent line projected and now under construction to New York City. <br><br>Early Settlements.  Ridgefield embraces the earliest settlements in the ancient township of Hackensack, antedating even the organization of that township in 1693, and of the county of Bergen in 1675.  There seems to have been no town or village compactly built, like the village of Bergen, but there were settlements both of Dutch and English in and about what was subsequently known as English Neighborhood prior to 1675.  The Westervelts, the Zimcrmans, the Bantas, and the Blauvelts, all coming from Holland, settled in the middle of the seventeenth century in that locality.  The ancestors of Jacob P. Westervelt, now of Hackensack Village, with himself, were born in English Neighborhood.  His father was born there in 1776, and was the son of Christopher Westervelt, who was born there certainly as early as 1690, and he was the son of the original ancestor of this family, who came from Holland and settled on Overpeck Creek, within the present limits of Ridgefield township, probably about 1670." Five Mile Landing is located on the east side of the Topock Marsh along the Colorado River. The Topock Marsh is one of the larger birdwatching sites found in the Lower Colorado River Valley, found from south of Hoover Dam to the Colorado River Delta in Mohave County, Arizona.  This public land is managed by the US Fish and Wildlife Service, and available to the public for recreational purposes. Hoover Dam, originally known as Boulder Dam from 1933 to 1947, when it was officially renamed Hoover Dam by a joint resolution of Congress, is a concrete arch-gravity dam in the Black Canyon of the Colorado River, on the border between the U.S. states of Nevada and Arizona.  It was constructed between 1931 and 1936 during the Great Depression and was dedicated on September 30, 1935, by President Franklin D. Roosevelt.  Its construction was the result of a massive effort involving thousands of workers, and cost over one hundred lives.  The dam was named after President Herbert Hoover.
Answer: Boulder Dam