When Price entered the state, he had about 13,000 men with him, many of which were poorly armed or had no weapons at all. The Confederate force included 14 cannons, but these were of
small bore, which limited their effectiveness against fortifications. Price's force was divided into three divisions, commanded by Major-General James Fagan and brigadier-generals John Marmaduke and
Joseph O. Shelby. Around 10,000 Union soldiers were scattered across Missouri, of whom about 3,000 were assigned to the St. Louis region, under the command of Brigadier-General Thomas Ewing Many of Ewing's men were in units of the
Missouri State Militia or the
Enrolled Missouri Militia. While many of the MSM men had
guerilla warfare experience, the EMM soldiers were poorly trained and equipped. Price learned that the town of
Pilot Knob and one end of the
St. Louis and Iron Mountain Railroad was held by Union troops while he was at
Fredericktown on September 24. Price did not want to leave a Union force free to operate in his rear, so he decided to move aggressively against the Union column. To accomplish this, he sent Shelby with his division north of Pilot Knob to disrupt the railroad on September 26, while sending Fagan and Marmaduke directly against the Union troops. Ewing commanded the Union force near Pilot Knob, which was 1,456 strong: 856 Union Army soldiers, 450 MSM men, and a group of 150 mobilized civilians. Additionally, Price learned on the 25th that Union Major-General
Andrew Smith and 8,000 men were near St. Louis, which caused him to doubt his ability to take the city. On September 26, Price began moving his army from Fredericktown towards the
Arcadia Valley, with Fagan's division in the lead. The entrance to the valley, Shut-In Gap, was unguarded, so Fagan sent Colonel
William F. Slemons's brigade, temporarily under the command of Colonel John C. Wright, forward. Wright, with about 250 men, surprised a small Union detachment, which managed to send a messenger warning a detachment of the
47th Missouri Infantry Regiment at
Ironton and the Union command at Fort Davidson, further north. Ewing responded by sending 80 men from the 3rd MSM Cavalry Regiment to investigate the reports. Wright's men scattered the MSM soldiers, but were repulsed by the detachment of the 47th Missouri Infantry when they tried to drive through Ironton. After hearing the sounds of battle from the valley, Ewing sent Major James Wilson and several hundred cavalrymen towards the fighting and later followed Wilson himself with a force from the
14th Iowa Infantry Regiment and two cannons from the
2nd Missouri Light Artillery Regiment. The two groups joined with the Union detachment already in Ironton around 15:00, attacked under the command of Wilson, and drove Wright back towards the gap. Ewing, under the impression that he was fighting with Shelby's men, left Wilson and his force in the valley and personally returned to Fort Davidson. He then made preparations to defend the fort against Confederate attack and send extra supplies up the railroad to Smith. As more Confederate troops passed through Shut-In Gap, Wilson realized that he was facing a very large enemy force. At around 22:30, Ewing gave Wilson permission to withdraw to a more secure position near Ironton. The reports also made Ewing unsure about the wisdom of attempting to hold Pilot Knob. That night, he asked several of his subordinates for their opinions about the best course of action. After some discussion, Ewing decided to hold the fort, influenced by the uncertainty of being able to hold the poorly trained portions of his force together during a retreat. The political aspirations of Ewing and Colonel
Thomas C. Fletcher of the 47th Missouri Infantry also contributed to the decision to fight it out, as a retreat was thought to be politically detrimental. The supplies and some civilians were evacuated via the railroad.
Fort Davidson as seen today. The crater from the powder magazine blast is visible on the far right. Pilot Knob is the hill at the back. Fort Davidson is near the town of
Pilot Knob, Missouri, which is located in a plain between four peaks:
Pilot Knob, Shepherd Mountain, Rock Mountain, and Cedar Hill. Fort Davidson was preceded by an earlier structure known as
Fort Hovey (later renamed Fort Curtis, after Major-General
Samuel Curtis), which was built by
Union Army soldiers in 1861 south of the future location of Fort Davidson. Fort Curtis was armed with four 32-pounder guns, three
24-pounder howitzers, and two
Coehorn mortars. Eventually, eight smaller artillery pieces were added to the fort. Fort Curtis's location was viewed as a disadvantage, as it was not located in a place where it could easily guard the important local iron deposits and a nearby railroad. Fort Davidson was constructed in 1863 near the base of Pilot Knob in order to better protect those features. Built in the shape of a
hexagon, Fort Davidson had earthen walls. In his book ''
Price's Lost Campaign: The 1864 Invasion of Missouri'', the historian Mark A. Lause stated that the fort's walls were long, while the historian Kyle Sinisi stated that they were long. These wall were either , as per Sinisi, or high, as per Fort Davidson's National Register nomination form and historian
Albert Castel. Two
rifle pits, also described as trenches, were constructed: one to the north and one to the southwest. The fort's
magazine was located in the inner portion of the fort and was located underground, with of dirt and some wood planking serving as protective covering. An 1864 inspection produced a report finding that the terrain of the mountains exposed defenders of Fort Davidson to potential
enfilade fire. Surrounding the fort was a moat. Castel and Lause state that the moat was around deep, the NRHP form provides the depth as and Sinisi and a writer for the Missouri Archaeological Society give a depth of . Fort Davidson was named for Brigadier-General
John W. Davidson, who had commanded Union troops in the area in 1862. ==Battle==