The Lyran Commonwealth was formed in 2341 as an amalgamation of three smaller mutual defense leagues: the Tamar Pact, the Federation of Skye, and the Protectorate of Donegal. The original Lyran capital was Arcturus. Shortly after the outbreak of hostilities between the Commonwealth and the Draconis Combine in 2407, however, the Lyran government moved to its current location on Tharkad. Soon after, leadership of the Commonwealth passed from Alistair Marsden to his wife, Katherine Marsden Steiner, and remains in Steiner hands to this day.

The Lyran Commonwealth currently consists of about 400 worlds. During the course of the first three Succession Wars, it has been slowly but steadily losing ground to the Draconis Combine, which had taken over a fourth of the original Lyran territories (including more than half the old Tamar Pact worlds).

One reason that House Steiner has remained a formidable force in Successor State politics even in the worst of times is that its domain includes some of the most richly endowed planets in the Inner Sphere. These include Alarion, Coventry, Donegal, Summer, Tamar, New Karlsruh, and Hesperus II. The latter is the site of the Star League's largest surviving military supply depots and the largest still-functioning 'Mech manufacturing and repair facility in the Successor States.

Regardless of its military fortunes, the Lyran Commonwealth has consistently maintained its reputation for making money. The Commonwealth's overall industrial output, particularly in non-military goods, outstripped that of the other Successor States. Even today, only the Free Worlds League surpasses the Commonwealth's GNP per capita. This economic strength has made the House Steiner currency the most stable in the Inner Sphere. Some of this success is due to human ingenuity, their rich natural resources of the average Lyran member-world and to the relatively small amount of war damage sustained by the industrial plants of a few, key remote worlds.

Over the years, the Archons of House Steiner have consistently sponsored innovative economic and trade policies, such as major tax advantages for industrial reconstruction projects, awarding land grants to successful entrepreneurs, and encouraging the activities of free traders. Many of these policies are still presently in force.