In the mid 1800s, the town of Leno was founded along the banks of the Santa Fe River. The first telegraph linking Florida to the outside world passed through Leno. In 1896, the railroad bypassed the tiny town, causing Leno¿s inevitable decline. Acquired in the early 1930s by the Florida Board of Forestry, the park was developed by the Civilian Conservation Corps (CCC) and the Works Progress Authority primarily for use as a summer forestry camp. Several of the original structures are still in use today. O¿Leno State Park is located on the banks of the scenic Santa Fe River, a tributary of the Suwannee River. The distinctive geological feature of the park is the River Sink where the Santa Fe River disappears underground to re-emerge three miles south at River Rise Preserve State Park.
Before the Florida Forest Service owned the land where O'Leno State park is located, the town of Leno prospered. The town, founded in 1840 on the banks of the Santa Fe River, was originally called Keno after a popular gambling game at that time. In 1876 Colonel Whetstone applied for a post office for the town of Keno and was denied due to the name and its relationship with gambling. The Colonel then had the name changed to Leno and was granted the post office, which he ran until 1890 when he moved to Mikesville, three miles north of Leno. Leno was an industrious town with two grist mills, a saw mill and six cotton gins. The town also had a general store, hotel, livery stable and doctor's office. The demise of the town took place in 1894 when the S, F & W Railroad was diverted to pass through Fort White instead of Leno. By 1896 everyone had moved away, leaving Leno a ghost town.
Although the town of Leno met its demise in the late 1800s, it was still a beautiful and popular place for the people of nearby towns and farms to meet for picnics and swimming. Referred to as 'Old Leno, it eventually became O'Leno , the name that it still has today.
After the demise of the town of Leno, the Florida Forest Service (by 1935, a division of the Board of Forestry and Parks) purchased the property where the town had been located. The site of O'Leno State Park was initially chosen as the location of a Florida Forest Service camp to provide forestry training and education. Development of the camp started as a Works Progress Administration (WPA) project using unemployed labor from the High Springs area. In July 1935, the Civilian Conservation Corps (CCC) installed workers from Company 418, Camp P-67, to assist WPA workers at O'Leno. Development of the site progressed rapidly and between 1935 and 1936 the CCC cleared land, built roads and trails and constructed the dining hall, pavilion, museum/tower building and suspension bridge. In late 1936, the CCC enrollees were withdrawn as the project neared completion and WPA labor became unavailable.
Camp O'Leno opened in 1938 as a Florida Forest Service training camp. The purpose of the training camp was to train employees and youth groups interested in forestry. The Forestry Service ran the training camp for two summers before turning the camp over to another division within the Board of Forestry and Parks, the Florida Park Service, making it one of Florida's first state parks.