The historic level of Lake Minnetonka was probably about 925 feet in elevation. A mill was established in 1853 near the present day intersection of Minnetonka Road and Plymouth Road just east of I-494. That mill included a dam that raised the level of Minnehaha Creek as much as 12 feet. This raised the level of Lake Minnetonka to about 932 feet in elevation. The higher water levels allowed packet boats to travel from the mill site to settlements along the lake.
The Minnetonka Mills closed in 1886 and burned in 1902. At some point during that interval, the dam at Plymouth Road was removed. To prevent the lake levels from falling too far, a wooden weir was built at this location in 1897. That structure was rebuilt in 1932 and again in 1944. A more significant headwater control dam was built in 1979. That that time, a study determined that the ideal lake level is 929.4 feet above sea level. The control structure is adjusted to maintain that level as much as possible. However, evaporation often has a greater impact on water levels, so the lake sometimes falls below this target level.
The Minnehaha Creek Headwaters Park and the Headwaters Control Structure were extensively remodeled in the mid-2000s. A deck was added in 2005, and the pedestrian bridge was added in 2006. The pedestrian crossing uses a long catwalk across Gray's Bay to connect to the regional rail system. The observation decks and picnic tables make for great places to stop and watch birds or do a little fishing.
The photo above is looking west towards the outflow side of the control structure. The pedestrian bridge is on the near side of the dam. The photo below is looking north towards the dam from the park on the south side of the bay.