A hydroelectric power plant on the Osage River was first pursued by Kansas City developer Ralph Street in 1912. He put together the initial funding and began building roads, railroads, and infrastructure necessary to begin construction of a dam, with a plan to impound a much smaller lake. In the mid-1920s, Street's funding dried up, and he abandoned the effort.
The lake was created by the construction of the 2,543-foot-long (775 m) Bagnell Dam by the Union Electric Company of St. Louis, Missouri. The principal engineering firm was Stone and Webster. Construction began August 8, 1929, and was completed in April 1931; the lake reached spillway elevation on May 20, 1931. From above, the lake is shaped somewhat like a dragon.
Originally built in 1930, the bridge crosses the Grand Glaize Arm of the lake in Osage Beach, Missouri. It carries U.S. Route 54 and connects Osage Beach to Camdenton. Originally, one girder bridge carried both directions of traffic; a second girder bridge was constructed in 1984, enabling traffic to pass over the lake in both directions using separate bridges. It has undergone a significant number of improvements since its original construction, and now supports three lanes of traffic in both directions.
A large number of bridges had been constructed for efficient crossing of the lake. Niangua Bridge, built in 1936, was replaced by a girder bridge in 2003. The Niangua Arm US 54 Bridge, built in 1931, was replaced by a girder bridge in 1999.
Originally constructed in 1931, Bagnell Dam is the only major dam supporting Lake of the Ozarks. Located in Miller County near Camden County, the dam is 2,543 ft (775 m) long and 148 ft (48 m) tall. The dam was originally constructed by the Union Electric Company (now Ameren) to provide hydroelectric power to the nearby Osage Powerplant (located near the base of the dam) and support two-way traffic on a narrow highway above the dam (Bagnell Dam Boulevard). Since its original construction, the dam has undergone a number of significant infrastructure upgrades throughout the 2010s. The dam has 12 floodgates, which fully open when the lake floods. In 2019, the floodgates were open due to the Lake of the Ozarks being hit by the flooding.
The Hurricane Deck Bridge is a delta-frame bridge located in the west side of Lake of the Ozarks. Stretching over 2,280.3 ft (695 m) long and 28.0 ft (9 m) wide, the bridge was established to connect Laurie with Camdenton. The bridge was originally constructed in 1934 as a truss-arch bridge, but this bridge was replaced in 2013. The first bridge's structure was similar to the structure of the I-35W Mississippi River bridge, which had collapsed six years before the bridge was destroyed. After the replacement opened in 2013, the original bridge was destroyed.
During the process of land acquisition for the lake during the 1920s, 17,500 acres (71 km ) of land were set aside for a national park along the Grand Glaize Arm of the lake. In 1946, this land was acquired by the State of Missouri for Lake of the Ozarks State Park, the largest state park in Missouri. Another state park on the shores of the lake is Ha Ha Tonka State Park on the Niangua Arm of the lake.
The Lake of the Ozarks Community Bridge is a continuous truss bridge in Lake Ozark. The bridge is over 2,695 ft (821 m) long and 72 ft (22 m) wide. Built in 1998, it is one of the newest bridges in the Lake of the Ozarks area, primarily built to connect the east (towards Lake Ozark and Osage Beach) and west sides (towards Sunrise Beach and Camdenton) of Lake of the Ozarks. Furthermore, the bridge is the only toll bridge in the Lake of the Ozarks area, with a toll that varies between seasons. The bridge is expected to stop tolls on April 30, 2024. The bridge was expected to be toll-free by 2026.
In 2011, the Federal Energy Regulatory Commission (FERC) renewed the lease for the power plant operated by Ameren Missouri. In the process, the FERC determined that numerous homes and structures were encroaching on utility land in violation of federal regulations. According to the Boston Globe, this issue "has triggered panic in the area's lakefront communities and led to a growing battle among regulators, a utility company, land attorneys, and the state's congressional delegation."
On April 1, 2012, biologist and TV personality Jeremy Wade visited the lake and filmed an episode on the large catfish that could be caught there.
In 2015, FERC issued an order allowing Ameren Missouri to pursue permits for about 215 structures that were termed as "nonconforming". Those were the structures remaining in limbo after Ameren was given approval to redraw the project lines encompassing Lake of the Ozarks.
The TV series Ozark is set in Osage Beach, though filmed in Georgia. In November 2017, it was reported that the series helped increase tourism and notoriety of the Lake of the Ozarks, but did not have a significant economic impact. In February 2018, a real-life restaurant called Marty Byrde's, inspired by the series, was opened in Lake Ozark, Missouri, and includes menu items based on the show, including Ruth's Smoked Wings.
Recently, the lake has been impacted by several extreme weather events. In 2019, the lake was hit by the floods. In 2021, the lake froze over during a cold wave, the first time the lake had frozen over in 20 years, according to Ameren Missouri. In 2022, the lake levels were low due to a drought.
In 2021, Osage Casino management announced it planned to build in the Lake of the Ozarks area. Construction had not begun, but demolition of the former Quality Inn was completed where the casino will be located. A house joint resolution has to be passed allowing a casino to be built near the Osage River has to signed before construction can began.
An amusement park named "Oasis at Lakeport" is planned to open in 2025. It will include a Marriott Hotel that is scheduled to open in 2026.