The Miami and Erie Canal was a canal that connected the Ohio River in Cincinnati, Ohio with Lake Erie in Toledo, Ohio. It consisted of 19 aqueducts, three guard locks, and 103 canal locks. Each lock measured by and they collectively raised the canal above Lake Erie and above the Ohio River. The peak of the canal was called the Loramie Summit and extended between New Bremen, Ohio to lock 1-S in Lockington, north of Piqua, Ohio. The system consisted of of canal channel and was completed at a cost of $8,062,680.07 in 1845. Boats were towed along the canal using either donkeys or horses walking on a prepared towpath along the bank. The boats typically traveled at a rate of four to five miles per hour.
An interesting topographical map showing the geography, path, and elevations of the entire canal is located in the Heritage Museum
located in the building housing the Shrine of the Holy Relics in Maria Stein, Ohio, a community located from the canal and just south of Grand Lake St. Marys.
Grand Lake St. Marys, an artificial lake west of St. Marys, Ohio was originally constructed as a reservoir to supply water for the canal. Lake Loramie in Shelby County also was constructed as a reservoir for the canal. Indian Lake in Logan County was greatly enlarged to provide a steadier supply of water for the Sidney feeder. All three lakes are still used for recreation.
A branch canal was constructed from the Miami and Erie Canal from Middletown, Ohio to Lebanon, Ohio, called the Warren County Canal. This branch was opened in 1840, but operable for less than 15 years before being abandoned.
A short branch, the Sidney or Port Jefferson feeder canal ran up the Miami valley from Lockington through Sidney to a dam just upstream from Port Jefferson.
Much of the Canal corridor remains a prosperous manufacturing area, with Interstate 75 and railroads providing the transportation rather than the canal.
One of the original locks (#17) is located in the Carillon Historical Park in Dayton, Ohio. An unrestored, but complete lock (#15) is located just off Main Street (State Route 571) in Tipp City. Remains of the Excello lock are still located in the Butler County Excello Locks Park near the intersection of State Route 73 and South Hamilton Middletown Road in Lemon Township.
Much of the original towpath served as the right-of-way for the Cincinnati and Lake Erie Railroad, an electric interurban streetcar that operated until 1940. Part of the right-of-way was converted to the Wright-Lockland Highway (now part of Interstate 75). 
From 1920 to 1925 six million dollars was spent to use the bed of the canal to build a downtown subway in Cincinnati. The surface was paved over to form Central Parkway. Funds ran out before the Cincinnati Subway was completed.
Urban redevelopment has eliminated the beginnings and ends of the canal. However, on the canal's south end there is a drained section located in St. Bernard, Ohio's Ludlow Park where the canal bed is still visible. The canal remains watered (and theoretically navigable for canoes or kayaks) in the rural region between Delphos, Ohio and St. Marys, Ohio. South of St. Mary's, it has degraded to form a shallow ditch in most places, though some ruined locks remain. Driving from north to south along Ohio Route 66, one sees pieces of the original canal in Delphos, at a small historic park located at the "Deep Cut," in St. Marys, OH, Lock Two (a hamlet mostly consisting of period brick buildings), New Bremen, OH, Minster, Ohio, Ft Loramie, Ohio, and Piqua, Ohio. The Miami and Erie Canal Deep Cut is a U.S. National Historic Landmark near Spencerville that was designated in 1964. Perhaps the most interesting is the Piqua Historical Area
where there is a replica canal boat and other canal-related items. The Delphos Canal Commission also has a canal museum located on Main Street.
In addition, visitors to Providence Metropark, near Grand Rapids in the northwest part of the state, are able to ride a replica canal boat as it goes through lock number 44. Lock 44 is an original Miami and Erie canal lock and Providence Metropark is the only place in Ohio in which visitors are able to travel completely through a functioning canal lock.
Other sites of interest are listed.
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The northern portion of the towpath (from Fort Laramie to Delphos and beyond) is used as a hiking trail. 
The massive west abutment of the Old Nine-mile Aqueduct over the Great Miami River is still present ca. upstream of the Taylorsville Dam east of Vandalia (Montgomery County). The aqueduct was destroyed by the Great 1913 Flood. The abutment terminates a fairly intact canal segment that extends at least north to Tipp City. This segment includes an intact concrete weir near the abandoned Vandalia water treatment plant (aka "Tadmore Station") and a ruined lock (#16, "Picayune") about halfway to Tipp City along Canal Road.