(covers information from several alternate timelines)
Archer IV was an inhabited earthlike planet, the fourth orbiting the primary 61 Ursae Majoris, and was itself circled by two moons. The first M-class world surveyed by the crew of the starship Enterprise NX-01, Archer IV was unpopulated when it was discovered in 2151. The planet was later named in honor of the ship's commanding officer, Starfleet Captain Jonathan Archer. (ENT: "Strange New World", "In a Mirror, Darkly, Part II" production art)
Archer IV's atmosphere was composed of seventeen percent oxygen and eighty-one percent nitrogen, also including trace elements of nitrogen dioxide and chloromethane. Boasting a fertile landscape including vast grasslands and snow-topped mountains, Archer IV was inhabited by a wide array of plant and animal lifeforms, including nocturnal marsupials, scorpion-like arachnids, fireflies, and fish. The planet, however, supported no indigenous intelligent lifeforms.
Initial landing parties in 2151 experienced rapidly changing weather patterns and fast-moving storms. Such inclement weather spread toxic pollen, released by the diverse fauna and flora, causing in Human and Vulcan visitors paranoia and decreased cognitive function. With no refuge from the effects of the pollen, the planet was considered to be uninhabitable. (ENT: "Strange New World", "Home", "Two Days and Two Nights")
Shortly before Travis Mayweather visited the ECS Horizon in January 2153, Charles Tucker III handed him a PADD which included a picture of Mayweather standing in a green field on Archer IV. (ENT: "Horizon")
Archer IV remained uninhabitable throughout the 22nd century. In the early 2200s, however, an antidote for the pollen was discovered. By 2268, more than seven hundred million people populated the planet. (ENT: "In a Mirror, Darkly, Part II" production art)
In an alternate timeline, Archer IV was the site of a battle in a Federation-Klingon War during the mid-2360s. At this engagement, the Enterprise-D emerged victorious against the Klingons. During a later confrontation with the Klingons, following the appearance of the Starship Enterprise-C from a temporal rift, a small Klingon task force arrived decloaked, prompting Commander William T. Riker to remark, "They shouldn't be so confident after the pasting we gave them on Archer IV." (TNG: "Yesterday's Enterprise")
The undesignated planet from "Strange New World" was ultimately named after Jonathan Archer, as revealed by the captain's 23rd century personnel file in the season four ENT episode, "In a Mirror, Darkly, Part II".
Enterprise writer/producer Mike Sussman, a long-time Star Trek fan, had wanted to find a way to link the NX-01's captain to the planet Archer IV, which had been previously mentioned in dialogue as a destination for the USS Enterprise-D in TNG: "Yesterday's Enterprise" (and was also the site of a Federation-Klingon battle in that episode's alternate timeline). Sussman, who co-wrote "Strange New World" and "In a Mirror, Darkly, Part II", thought that it would be a fitting tribute for the Federation to name the planet after the first Human captain to explore it, and established the connection to Archer IV in text that he wrote for Archer's Starfleet file. That text was given by Sussman to the ENT art department, and was seen on a computer monitor aboard the 23rd century USS Defiant in "In a Mirror Darkly, Part II."
Archer's file further established that the fictional Archer IV orbited a real star, 61 Ursae Majoris, a detail previously mentioned in scene description in Sussman's script for the episode, "Home", which stated: "Archer points to a star (61 Ursae Majoris) near the Big Dipper." Archer then tells Erika Hernandez, "There... just to the left of Polaris. We found our first M-Class planet around that star."
The identification of 61 Ursae Majoris, 31 light-years from Sol, as Archer IV's home system is consistent with events from ENT: "Two Days and Two Nights", in which the NX-class Enterprise becomes the first Starfleet ship to travel ninety light years from Earth to the planet Risa. Archer IV was visited by Enterprise prior to its historic feat.
The script for "Strange New World" describes the then-unnamed world as a "lush, blue-green planet." In an unused line of dialogue from the script, the planet's mountains were described by Crewman Novakovich as seemingly taller than the Himalayas.
An official tie-in sourcebook "misidentified" Archer IV and its host star. Star Trek: Star Charts ("United Federation of Planets I," pp. 60, 63), which was published prior to the airing of "In a Mirror, Darkly, Part II," identified the "Strange New World" planet as Loracus Prime, which was a misinterpretation of text seen in a prop textbook in the beginning of that episode. The sourcebook went on to erroneously designate the star that Archer IV orbited as "Archer", placing it near Klingon territory, several hundred light years away from Sol and far outside the 90 light year range that Enterprise NX-01 had traveled in its first year. The more recent Stellar Cartography: The Starfleet Reference Library corrected this error. Both sourcebooks locate the 61 Ursae Major system in the Beta Quadrant; in the late 24th century, it was a Federation system.
The Star Trek Encyclopedia (4th ed., vol. 1, p. 38) states the exterior scenes, depicting the planet's surface, were filmed on location at the Golden Oak Ranch (aka the Disney Ranch) in Santa Clarita, California. The cavern interiors were filmed on location at the Bronson caves in Los Angeles. Prop stalagmites on wheels were brought to the location by the production to give the real cavern a more exotic, alien look; these fake stalagmites can be identified in the final episode as having a shiny, plastic-looking appearance.
The Pocket DS9 novel The 34th Rule stated Archer IV was the source of a beverage called Archerian slug wine (β). Although the novel was published two years before the episode aired, a species of slug-like creatures appear in "Strange New World".