I am writing (very slowly) an article on Mormon horns. The way things look to me now, it seems that “Mormon horns” were mostly a verbal, rather than graphical, phenomenon. That is, the idea that Mormons have/had horns seems to have been transmitted mostly through oral and written accounts rather than by the distribution of images. Such images did exist, however, and the purpose of this post is to collate all the horned-Mormon graphics I have identified and solicit further examples. (Note: clicking on most of the images below will link to higher resolution graphics.)
To my knowledge, the first graphic representation of a horned Mormon appeared in 1858. The New York-based Yankee Notions printed an illustration entitled “Ye Popular Idea of Brigham Young and his Followers.” It shows Brigham Young as an anthropomorphic male goat waving to a crowd of enthusiastically-cheering women and kowtowing horned males with an ironic “Liberty” flag waving over all. 
An 1860 Vanity Fair article entitled “Latest from Polygamutah” portrayed Brigham Young as a partially blind-folded figure—with goat horns, a goat-like beard, and one goat-like leg—hold pan pipes labeled “Polygam.” and gesturing toward a sign that reads “Notice: All Gentiles found on these premises shall be shot. …Brig. Young.” 
In 1879 the San Francisco Wasp printed “Situation of the Mormons in Utah,” a section of which showed Brigham Young and other leaders with prominent horns (see detail below).  “Situation” is the only nineteenth-century image I have identified that clearly shows fully-human Mormons with horns.
In 1882 the Wasp again presented horned Mormons, but this time with biological goats.  In “Uncle Sam’s Nightmare,” a sleeping Uncle Sam is weighed down by a “Chinese Question” dumbbell and a male goat labeled “Polygamy.” In the background Chinese males and female goats—wearing sun bonnets and representing plural wives—look on.
The New York Daily Graphic took a focused interest in Mormonism in the early 1880s. From 1883 August 21 to Dec 12 it showed Mormonism on its cover nine times. Four of those covers featured what Bunker and Bitton described as “a defiant, unscrupulous Mormon.”
For present purposes, the figure’s most important features are horns and pointed ears—unambiguous in one case (bottom left) and suggestive in two others (top right, bottom right).
One other of The Daily Graphic’s Fall 1883 Mormon cover images had horns, but it was a non-humanoid dragon.
A horned (or at least prominently tusked), metaphorical Mormonism had also appeared as an illustration in The Daily Graphic in 1881. 
Another horned-dragon appeared in Minnesota in 1904. 
In 1885 Thomas Nast published an image showing a male ruffian, armed with a hatchet, guarding a room marked “The Mormon Harem.” The guard has “hair horns”: his hair is standing up in a way that suggests horns and his facial features suggest a demon. 
…and that exhausts my collection of graphical images of horned Mormons. Compared to the total volume of Mormon graphic images in the nineteenth century, I did not find very many pictures of Mormons with horns.
So, gentle-readers, what other graphical images of horned Mormons do you know of before, say, 1950?
 On its face, the illustration (with caption) is an early report that some people in the region around New York believed that some Mormon males had horns. Of course, satirical drawings should not be taken literally. It is not even clear what, exactly, the intended purpose of the illustration is. On the one hand, the artist mocks the irrational, hyperbolic conception of Mormonism presumably held by some New Yorkers. On the other hand, it portrays and probably perpetuates an irrational, hyperbolic conception of Mormonism. “Ye Popular Idea of Brigham Young and his Followers.” Yankee Notions, 1858 April. Bunker and Davis commented on the image: “When Yankee Notions printed “Ye Popular Idea of Brigham Young and his Followers” in April, 1858, it effectively distilled the contemporary view of the Mormons (illustration 10).26 At the same time the illustration demonstrated the power of pictorial shorthand to convey a number of ideas. The goat caricature of Brigham Young was a symbol of lust. The horns of some of the prostrate followers was not a new idea, but was an early graphic representation of that image. [n27] The enthusiasm of the females in the background, apparently for Brigham Young, was one of many stereotypes of Mormon women, some of which went directly contrary to this view. The wild-eyed facial expressions on the adherents to this singular faith underscored their peculiarities. And the flag of liberty in the midst of the Mormons was a parody of the ‘indiscriminate allegiance’ of the submissive followers.” [n27 cites Karl E Young, “Why Mormons Were Said to Wear Horns,” in Thomas E Cheney, ed, Lore of Faith and Folly (Salt Lake City: University of Utah Press, 1971), 111-12, and the Wilson Law quote (HC 5:214). Gary L Bunker and Davis Bitton, “Illustrated Periodical Images of Mormons, 1850-1860,” Dialogue: A Journal of Mormon Thought 10.3 (1977 Spring): 90 (82-94).
 The article reported (presumably with tongue-in-cheek) that Brigham Young had become reclusive and taken to wearing a blindfold because he had “long been playing a game of ‘blind man’s buff’ [sic] with the government” and because there were so many murders that he “keeps the blinker on so as to be blind to what is going on about him.” It described Utah Territory as “demi-semi-demoniac Polygamutah” and asserted that: “Territories are less savage when abandoned to their primitive bears and indigenous buffaloes, than when subjected to the half-civilized influence of such a socialism as the Mormon megatherium: and we doubt if the Valley of the Lake of Salt, in the days when no footmarks fell on its crystal-frosted soil save those of the fierce beast of the mountain and plain, ever displayed, half so beastly a sight as that of the grizzly goat-herd, Brigham, leading his hoofed and horned flock to the sound of his Pandean, polygan pipe.” The article is “Latest from Polygamutah” and the image is “The Veiled Prophet of Polygamutah”; both are on the same page of Vanity Fair 1 (1860 Feb 11): 100. In the article the pipes are described as “polygan” while in the image the label is “polygam.” According to Bunker and Bitton, citing Weitenkampf, one HL Stevens “did the cartoons for Vanity Fair.” (Gary L Bunker and Davis Bitton (The Mormon Graphic Image, 1834-1914 (Salt Lake City: University of Utah Press, 1983), 30), citing Frank Weitenkampf (American Graphic Art (New York: Macmillan, 1942), 228)).
 Detail from “Situation of the Mormons in Utah,” The Wasp, San Francisco, CA, 1879 Feb 01, page number not given.
 No artist listed, “Uncle Sam’s Nightmare,” The Wasp, San Francisco, CA, 1882 Mar 24, page number not given, image courtesy of the University of California.
 “defiant, unscrupulous” comes from Bunker and Bitton, Graphic Image, 114, discussing “The Remaining Twin,” top right. The images are, top left to top right: No illustrator listed, “The Modern Bluebeard,” drawing, no caption, The Daily Graphic 32.3232 (1883 Aug 21 Tue): 339 (cover). No illustrator listed, signed “C.S.R.” [Charles Stanley Reinhart], “The Remaining Twin,” drawing, caption: “Uncle Sam: ‘I don’t know exactly what to do with that fellow. I must decide before he decides what to do with me.’” The Daily Graphic 32.3279 (1883 Oct 15 Mon): 763 (cover). Bottom left to bottom right: No illustrator listed, signed “Cusachs” [Philip G Cusachs], “Shall Not That Sword Be Drawn?,” drawing, no caption, The Daily Graphic 32.3288 (1883 Oct 25 Thu): 843 (cover). No illustrator listed, signed “Cusachs” [Philip G Cusachs], “The Questions of the Hour,” no caption, The Daily Graphic 33.3321 (1883 Dec 04 Tue): 251 (cover).
 The figure was male, armed, and wearing outdoorsman clothes including boots and a broad hat. In one image, life-sized women are tied behind his horse; in another, half-height women are tied to his belt or are being dragged by the hair; in the last two, quarter-height women are suspended by the hair from his belt. Three of the figures have feathers in their hats, which are almost certainly meant to suggest savagery or sub-humanity via similarity to Native American Peoples. The facial expression is fierce, the beard unkempt.
 [Beast with no horns but large tusks]: “Complete the Work Begun by the Republican Party Twenty Years Ago,” The Daily Graphic 8 (1881 Feb 18), cover. No illustrator listed, “What Shall They Do to Be Saved?” drawing, caption: “The Edmunds Law is a failure — What shall Uncle Sam do next?” The Daily Graphic 33.3294 (1883 Nov 01 Thu): 1 (cover), image courtesy of “Old Fulton New York Post Cards,” fultonhistory.com.
 H Hubert, political illustration, “The Salt Lake Monster Not Yet Extinct,” Duluth Evening Herald, Duluth, MN, 1904 Mar 05 Sat, Last edition, §1, p 1.
 Thomas Nast, “The House That Needs Dusting Very Much,” Harper’s Weekly 29.1475 (1885 Mar 28): 208, image courtesy of HarpWeek. A large duster labeled “Set up and…” is extending through a window toward the guard, who reacts defensively. An unidentified building is visible through the window. For other examples of “hair horns,” see “Abe Lincoln’s Last Card; or, Rouge-et-Noir,” Punch, or The London Charivari 43 (1862 Oct 18): 161 [Lincoln has “hair horns,” discussed below], and Bernhard Gillam, “Foes in his path – the herculean task before our next president,” Puck 16:415 (1885 Feb 18): 392-393 (centerfold), courtesy of the Library of Congress; [Jay Gould (left side, belt labeled “Land Grabber,” holding a club labeled “Monopoly”) has hair horns.]