Discovered by Pierre Méchain on August 27, 1780.

Charles Messier: October 18, 1780. 75. 19h 53m 10s (298d 17' 24") -22d 32' 23"
Méchain: (298d 17' 30") -22d 32' 00"
"Nebula without star, between Sagittarius & the head of Capricorn; seen by M. Méchain on August 27 & 28, 1780. M. Messier looked for it on the following October 5, & on October 18, compared it [i.e., its position] with the star 4 Capricorni, of sixth magnitude, according to Flamsteed: it seemed to M. Messier to be composed of nothing but very small [faint] stars, containing nebulosity: M. Méchain reported it as a nebula without stars. M. Messier saw it on October 5; but the Moon being above the horizon, & it was not until the 18th of the same month that he was able to judge about its form & determine its position."

Frederick William Herschel: [PT 1814, p. 279; SP2 p. 538]
Connoiss. 75 [M 75 = NGC 6864] is "A globular cluster of stars, and is a miniature of the third [M 3]."

[PT 1818, p. 448-449; SP2 p. 600]
The 75th of the Connoissance. [M 75 = NGC 6864]
"1799, 7 feet finder. It is just but visible."
"1799, 7 feet telescope. There is not the least appearance of its consisting of stars, but it resembles other clusters of this kind, when they are seen with low space-penetrating and magnifying powers."
"1810, 10 feet telescope. With 71 it is small and cometic."
"1784, 1785, 20 feet Newtonian. Easily resolvable; some of the stars are visible."
"1810, 20 feet, front view. It is a globular cluster."
"1799, 1810, large 10 feet. Its diameter with 171 is 1' 48"; with 220 it is 2' 0"."
By the observation of the 20 feet Newtonian telescope, the profundity of this cluster must be of the 743d order.

John Frederick William Herschel: h 2064 = M75.
Sweep 369 (September 3, 1831)
RA 19h 56m 2.5s, NPD 112d 23' 31" (1830.0) [Right Ascension and North Polar Distance]
vB; R; vsvmbM; 2'; a bright R ball 15" diam, in an atmosphere 2'; 320 does not show the stars but makes it more resolvable.
very bright; round; very ssuddenly very much brighter toward the middle; 2' [diameter]; a bright round ball of 15" diameter, in an atmosphere of 2'; [magnification] 320 does not show the stars but makes it more resolvable [mottled].

Sweep 298 (September 22, 1830)
RA 19h 56m 2.7s, NPD 112d 23' 38" (1830.0) [Right Ascension and North Polar Distance]
pB; R; psvmbM; r; 90".
pretty bright; round; pretty ssuddenly very much brighter toward the middle; round; 90" [diameter].

Sweep 275 (July 28, 1830)
RA 19h 56m 2.9s, NPD 112d 24' 10" (1830.0) [Right Ascension and North Polar Distance]
Not B; S; R; psbM; 2' diam; r, but not resolved. An insignificant object.
Not bright; small; round; pretty suddenly brighter toward the middle; 2' diameter; mottled, but not resolved. An insignificant object.

William Henry Smyth: DCCXXX [730]. M75. DCCXXX. 75 M. Sagittarii.
AR 19h 56m 38s, Dec S 22d 22'.0
Mean Epoch of Observation: 1834.62 [Aug 1834]
A globular cluster in the space between the left arm of Sagittarius and the head of Capricorn, and 7deg 1/2 degrees to the south-south-west of Beta Capricorni. It is a lucid white mass among some glimpse stars, with a large [bright] one in the nf [north following, NE] verge field. It was discovered by Pierre Mechain in 1780, who considered it as a nebula without stars; but Messier viewed it as a mass of very small stars, which opinion, on an object which at best is rather faint, was bold. In 1784, it was resolved by William Herschel's 20-foot Newtonian, and, on being gauged, was assigned a profundity of the 734th order. No wonder that this miniature of 3 Messier [M3] (No. CCCCXCII [492]) should be pale to gaze.

John Herschel, General Catalogue: GC 4543 = h 2064 = M75.
RA 19h 57m 49.1s, NPD 112d 18' 47.5" (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl.; B; pL; R; vmbMBN; rr. 10 observations by W. & J. Herschel.
Globular cluster; bright; pretty large; round; very much brighter to the middle where there is a bright nucleus; partially resolved/some stars seen.

John Louis Emil Dreyer: NGC 6864 = GC 4543 = h 2064; Méchain, M 75.
RA 19h 57m 49s, NPD 112d 19.0' (1860.0). [Right Ascension and North Polar Distance]
Glob. Cl., B, pL, R, vmbMBN, rr; = M75
Globular cluster, bright, pretty large, round, very much brighter to the middle where there is a bright nucleus, partially resolved/some stars seen.

Heber Doust Curtis: [Descriptions of 762 Nebulae and Clusters photographed with the Crossley Reflector. Publ. Lick Obs., No. 13, Part I, p. 9-42]
NGC 6864, RA=20: 0.2, Dec=-22:12. M. 75. Bright compact globular cluster 2' in diameter. Greatly condensed at center. 9 s.n.