Tellar Prime

Tellar Prime or Tellar was the inhabited prime planet in its star system. This was the homeworld of the Tellarites, a warp-capable humanoid species.

Relative to the planetoid Babel, Tellar was located on the far side of the Andorian Empire. 

Good arguments were considered a sport on Tellar. 

In November 2154, visited Tellar Prime to pick up a Tellarite delegation and transport them to Babel. 

In 2155, representatives from Tellar took part in talks on Earth to form a Coalition of Planets. In 2161, Tellar became a founding member of the United Federation of Planets. 

Following the fall of Betazed during the Dominion War, in 2374, Tellar was considered to be vulnerable to a Dominion attack. 

In a possible 3186 experienced by Gabrielle Burnham, Tellar Prime was one of the worlds where all life had been eradicated by .

Background information
While conceiving, D.C. Fontana wrote, in a developmental document, "Tellar is a savagely cold planet." The extreme coldness of the planet was intended to account for the Tellarites having lots of fur on their bodies. While this is reminiscent of what the Andorian homeworld would turn out to be, the only canon depiction of Tellar Prime in ENT: "Babel One" shows at least a portion of the planet to be seemingly temperate, with at least one open body of water (which is actually a depiction of southern Lake Michigan) among what appears to be green vegetation.

Apocrypha
According to Star Trek: Star Charts, (pp. 18, 19, 36, & 44) and Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), the Tellar (61 Cygni) system was located in the Tellar Sector (Sector 007), a region of space in the Alpha Quadrant. The system was a binary system with a pair K-class stars. In the 22nd century, this system was a destination on an Earth trade route.

According to Stellar Cartography: The Starfleet Reference Library ("Federation Historical Highlights, 2161-2385"), Tellar was a planet orbiting Tellar A (61 Cygni A). The planet had two moons, named Kera and Phinda. Its official name was United Planets of Tellar Prime. Alternative names for this planet were Tellar Prime, Miracht, Pangeos V. The planet's capital was Shirgat. Tellarites were the primary species. In the late 24th century, the planet had a population of 2.3 billion. This planet was warp-capable in 1959.

The Worlds of the Federation reference book (p. 20) states Tellar to be the fifth planet of the 61 Cygni system. It also gives Miracht as an alternative name for the planet and lists two moons called Kehra and Phinda.

The Star Trek Star Fleet Technical Manual (T0:00:01:19) lists the United Planets of 61 Cygni as one of the founding members of the Federation.