[1] The first-published work in the series, which was Niven's first published piece, was "The Coldest Place", in the December 1964 issue of If magazine, edited by Frederik Pohl.
In the future that the series depicts, spanning roughly the third millennium, humans have explored this region and colonized many of its worlds.
The earlier, Belter period features solar-system colonization and slower-than-light travel with fusion-powered and Bussard ramjet ships.
Stories earlier in the timeline feature technology such as Bussard ramjets and drouds (wires capable of directly stimulating the pleasure centers of the brain), and explore how organ transplantation technology enables the new crime of organlegging (as well as the general sociological effects of widespread transplant technology), while later stories feature hyperdrive, invulnerable starship hulls, stasis fields, molecular monofilaments, transfer booths (teleporters used only on planetary surfaces), the lifespan-extending drug boosterspice, and the tasp which is an extension of the droud which works without direct contact.
Developed by the Institute of Knowledge on Jinx, it is said to be made from genetically engineered ragweed (although early stories have it ingested in the form of edible seeds).
In Niven's first novel, World of Ptavvs, the hyperdrive used by the Thrintun required a ship to be going faster than 93% of the speed of light.
In the vast majority of Known Space material, hyperdrive requires that a ship be outside a star's gravity well to use.
In Juggler of Worlds, the Puppeteers, attempting to surmise how this was done without antimatter, identify another technique which can be used to destroy the otherwise invulnerable hulls, one which does suggest some potential defense options.
On Earth in the mid-21st century, it became possible to transplant any organ from any person to another, with the exception of brain and central nervous system tissue.
A Slaver stasis field creates a bubble of spacetime disconnected from the entropy gradient of the rest of the universe.
Time slows effectively to a stop for an object in stasis, at a ratio of some billions of years outside to a second inside.
The stepping disks are an outgrowth and improvement of the transfer booth technology used by humans and other Known Space races.
"Plateau Eyes" (introduced in A Gift From Earth) is an ability on the part of some to hide in plain sight, by causing others not to notice them.
The Pierson's Puppeteers engineer a lottery for child licenses on Earth to increase the occurrence of "luck", which they think is a paranormal ability humans have that has enabled them to defeat races such as the Kzinti.
In Ringworld, the character Teela Brown is said to have this ability (although possibly not to the same extent as others who avoided being included in the expedition).
ARM originated as an acronym for "Amalgamation of Regional Militia", though this is not a term in current usage by the time of the Known Space novels.
[10] An agent of the ARM, Gil Hamilton, is the protagonist of Niven's science fictional detective stories, a series-within-a-series gathered in the collection Flatlander.
Their basic function is to enforce mandatory birth control on overcrowded Earth, and restrict research which might lead to dangerous weapons.
By the 25th century, ARM agents were kept in an artificially induced state of paranoid schizophrenia to enhance their usefulness as law enforcement officials, which led to them sometimes being referred to as "Schizes".
Agents with natural tendencies toward paranoia were medicated into docility during their off duty hours, through the aforementioned science of psychistry (see Madness Has Its Place and Juggler of Worlds).
In the Known Space stories, Niven had created a number of technological devices (GP hull, stasis field, Ringworld material) which, combined with the "Teela Brown gene", made it very difficult to construct engaging stories beyond a certain date—the combination of factors made it tricky to produce any kind of creditable threat/problem without complex contrivances.
[1] Late in that decade, Niven invited other authors to participate in a series of shared-universe novels, with the Man–Kzin Wars as their setting.
Niven also states that this is not an invitation to violate his copyrights, warning potential publishers and editors not to proceed without permission.