Main Park Plaque:
Symmes Monument / Hollow Earth Theory
I Declare the earth is hollow, and habitable within," said John Cleves Symmes in summarizing his Theory of Concentric Spheres and Solar Voids" to a doubting scientific world in the early 1920's.
His theory is commemorated by this monument, topped by a replica of a hollow earth. Symmes believed plant and animal life existed within the opening of the hollow earth. The opening was called the Symmes Hole. The former army officer tried to persuade the U.S. Congress to finance hollow – earth exploration. After an exhausting lecture tour on behalf of his theory, Symmes died May 29, 1829, on his Butler County farm. He was buried here in the pioneer Hamilton cemetery, which Israel Ludlow had provided when he laid out the town in the 1790's. The theorist was the nephew of Judge John Cleves Symmes (1741 – 1814), who promoted settlement in this region after buying land north of the Ohio River between the Little Miami and Great Miami rivers.
When Greenwood Cemetery was created north of Hamilton in 1848, many of the remains in the Hamilton graveyard were removed to the new cemetery, but Symmes' body remained in its original location. In 1873, his son, Americus Symmes, obtained permission to erect a monument in the Fourth Ward park. A $16,000 renovation, commissioned by Historic Hamilton Inc., was completed in 1991.
Plaques on monument:
Capt. John Cleves Symmes entered the Army of the U.S. as an Ensign in the year 1802. He afterward rose to the rank of Captain, and performed daring feats of Bravery in the Battles of Lundy's Lane and sortie from Fort Erie.
Capt. John C. Symmes a native of New Jersey died in May 1829 Aged 49 yrs. & 6 months.
Capt John Cleves Symmes as a Philospher, and the originator of 'Symmes Theory of Concentric Spheres and Polar voids! He contended that the Earth is hollow and habitable within.
Note: His birth date (5 November 1780) and death date (29 May 1829) are listed as reported in  Ohio Valley Historical Series, Number Four, McBride's Pioneer Biography, Vol. II, Sketches of the Lives of some of the Early Settlers of Butler County, Ohio, by James McBride, published by Robert Clarke & Co, Cincinnati, 1871, pages 232-252, and  "John Cleves Symmes, the Theorist (First Paper)"by Elmore Symmes in Southern Bivouac: A Literary and Historical Magazine. Louisville, KY: Home and Farm Publishing Company. 2 (9), February 1887. pages 555–566. A different year (1779) of birth is reported in The Symmes Memorial: A Biographical Sketch of Rev. Zechariah Symmes, Minister of Charlestown, 1634-1671, with a Genealogy and Brief Memoirs of Some of His Descendants And an Autobiography, by John Adams Vinton, published by David Clapp & Son, Boston, MA, pages 95-98.
Aged 49 yrs. & 6 months