Looking south across the northeast gate block, August 3, 1937. Notice the extensive formwork required before concrete is poured. Reinforcing steel rods protrude vertically at left for the west wall of the lock gate recess. The formwork creates a large open area under the top slab for the long horizontal gate arm when the gate is open. The control house for this gate will be built above the horizontal reinforcing rods in the foreground. (MWRD photo 23434)

August 3, 1937. “209E” painted on the steel sheeting identifies cell number 209 of the east cofferdam. Looking northeast at the northeast lock gate recess shows that much of the concrete work has been completed and installation of the gate track is beginning. The large opening at the base of the wall right of center and the gate on the wall left of center is the inlet and outlet, respectively, for maintenance flushing of the gate recess. (MWRD photo 23436)

Looking east, August 30, 1937. The upper lock gate hinge is supported by the fabricated structural steel assemblage in the center, which will be encased in concrete. The upper hinge supports less of the gate weight but is important to control the horizontal motion of the gate. Across the gate recess, concrete work on the east wall of the recess has been completed. (MWRD photo 23479)

Looking southwest into the recess for the southeast lock gate, September 8, 1937. Adjustments are being made at lower left in the elevation of the gate track, while at lower right, reinforcing steel is being placed behind the gate pintle. The pintle allows the gate to swing while supporting much of the gate weight. At top center, finishing touches are being made to the concrete base for the gate operating mechanism. (MWRD photo 23801)

Looking north toward Navy Pier, August 30, 1937. Erection of the northeast lock gate begins. Two bottom trusses of the gate form a “V” pointing to the pintle and two riveted panels rise to the hinge. Formwork for the control house is being erected at left while other structural steel members for the lock gate lie on the lock floor. (MWRD photo 23481)

September 27, 1937. Completion of the erection of the northeast lock gate nears. The pintle and upper hinge is at left, flanked by the two open sides of the triangular gate. The open sides allow the gate to move easily through the water. Notice the curved track in center foreground, the gate is supported by rollers that bear on the track. The edge of the southeast lock gate is at right. (MWRD photo 23571)

Looking northeast, August 30, 1937, from the concrete mixing tower over the west gate block. The nearly completed northwest lock gate sits in its recess, the northwest control house is closed in, and the southwest control house is under construction in the foreground. In the left background, the navigation light stands at the east end of the federal north pier. (MWRD photo 23485)

Four weeks later on September 27, 1937, the northwest lock gate is undergoing final adjustments. The control house is in the upper left corner and to its right is the lock gate operating mechanism consisting of an electrical motor and gear reduction unit. A pinion gear below the operating mechanism rotates against a rack mounted on a long arm attached to the lock gate to open and close the gate. (MWRD photo 23573)

September 27, 1937. The northwest lock gate is in the closed position as viewed from southeast. The solid third side of the gate is a barrier to holdback higher lake water when the gate is closed. The lock gate operating mechanism is wrapped in a protective tarpaulin, indicating it is not yet being used. For adjustment and testing purposes, the gate is being moved with a cable and winch. (MWRD photo 23574)

Looking east, September 27, 1927. Both west lock gates are in the closed position. The track for the gates is embedded in the top of the curving curb beneath each gate. A roller assembly is shown on each side of the two people standing at the bottom of the gates. A vertical metal plate on each side of the roller sweeps debris off the track as the gate moves. (MWRD photo 23576)

September 27, 1937. The northwest lock gate hinge as seen from below. The pintle at bottom is hidden from view and the upper hinge is partially visible. At left, the staff gauge embedded in the wall indicates that the top of the wall is seven feet above CCD. The top of the solid face of the lock gate in Photo 2.63 is six feet above CCD. Both tops are several feet above historic high levels of Lake Michigan. (MWRD photo 23577)

Looking east from the top of the mixing plant, September 27, 1937. Most of the side walls of the lock chamber have been completed and water fills the space between the walls. The east and west cofferdams remain in place while work continues on the east and west lock gates. (MWRD photo 23578)

Eight months later on June 7, 1938, from the same point, the east cofferdam has been removed, the east lock gates are closed, the east guide walls have been extended, and the one remaining gap in the south lock wall is being completed. In the foreground, the southwest lock gate is in its recess and part of the west cofferdam remains while finishing work is in progress. (MWRD photo 24122)

Work was also underway to complete the south wall, and by June 7, 1938, a bulk cargo vessel was unloading rock to fill the wall. The wall will be capped with concrete. The former US Naval Armory on East Randolph Street is at left while the Tribune Tower and Wrigley Building stand out in the right background. (MWRD photo 24128)

The Chicago River Controlling Works lock and associated guide walls were completed by August 30, 1938, but as viewed from the US Coast Guard station looking east, a gap remained where the north wall and sluice gates will be constructed. The gap was needed for the passage of boats while the lock was being constructed. Sealing the federal north pier, shown at left, and the federal inner breakwater also remained to be completed. (MWRD photo 24351)

September 1, 1939. Both sets of lock gates are competed and ready for operation. The west lock gates are shown looking south. Each gate was operated by an electrical motor and a gear reduction unit, which was situated safely above the highest water level. Below the unit, the horizontal arm pushed the gate closed and pulled the gate open. (MWRD photo 24946).

Looking west from the east end of the southeast guide wall toward the Chicago skyline, September 1, 1939. The east lock gates are closed awaiting the passage of a boat behind the lock gates. The shorter northeast guide wall with a navigation light tower is shown at right. (MWRD photo 24954)

Looking west on the evening of October 19, 1939. Two tugboats are west-bound leaving the lock, while towing a prefabricated tube for the construction of the State Street subway under the Chicago River. The tubes were prefabricated in a drydock on the Calumet River. (MWRD photo 25100)

February 2, 1940. During the first full winter season of operation at the Chicago River Controlling Works, ice fills the 80-foot width of the lock chamber. Looking east from the midpoint of the lock chamber, the east lock gates are partially open. (MWRD photo 25501)

Ice in the recess of the lock gate pocket can impair gate operation. Shown on February 2, 1940, successive lock gate operations compress ice against the back wall of the recess and will not allow the lock gate to fully open. When not fully open, the lock gate protrudes into the lock chamber and may be struck and damaged by moving boats. (MWRD photo 25503)

September 18, 1940. Even though the lock at the Chicago River Controlling Works was in operation, work remained to seal the federal inner breakwater and north pier. Work recently began on the former. Looking south from southwest lock guide wall, sheet piling is being driven along the lake side of the inner breakwater. The location of the US Coast Guard Station precludes piling on the river side of the breakwater. (MWRD photo 26337)

By October 1, 1940, the sheeting has been driven to a point beyond the US Coast Guard Station where it passes through the breakwater. Looking south from the same point as in the prior photograph, the sheeting is braced with tie rods to the breakwater and the intervening space is being backfilled with impermeable clay to seal the breakwater. Rock backfill will be placed on the lake side of the sheeting for additional support. (MWRD photo 26396)

Looking north at the point where sheeting passes through the federal inner breakwater, October 1, 1940. The breakwater is a rock-filled timber crib securely founded on the lake bottom with timber piles, topped with a concrete cap and wall, to diminish wave intensity and calm water movement. The breakwater was not designed to be impermeable. (MWRD photo 26397)

Looking easterly toward the west side of the federal inner breakwater at the point where the sheeting passes through the inner breakwater and continues south to the south wall, October 1, 1940. The District had to make the breakwater impermeable to prevent river water from flowing through the breakwater into the lake. (MWRD photo 26399)

October 21, 1940. Installation of the sheeting has been completed on the river side of the federal inner breakwater. Looking north from south wall, the space between the sheeting and breakwater will be backfilled with impermeable clay. Rock backfill will be placed on both the lake and river sides for additional support. (MWRD photo 26448)

Sealing the federal north pier followed the same construction method as the inner breakwater. Looking east along the pier, October 7, 1940, the contractor is driving steel sheeting into the lakebed several feet north of the pier. To the right of the north pier navigation light tower it can be seen that the north wall enclosing the inner harbor has been completed. (MWRD photo 26387)

Steel tie rods connecting the concrete pier cap to the sheeting are being installed on October 7, 1940, to hold the top of the sheeting in place while the space between the sheeting and pier is backfilled with impermeable clay. Looking east along the pier, the so-called “dime” pier is in the left background. (MWRD photo 26388)

October 21, 1940. Sealing of the federal north pier is complete, with rock backfill placed against the steel sheeting and covering the clay. It is noted that the north basin wall and sluice gates at right of center behind the pier railing is also completed. The entire Chicago River Controlling Works is complete and will serve for 60 years until major modifications are made in 2000. (MWRD photo 26454)