The railway systems of the individual German states prior to the founding of the German State Railways (Deutsche Reichsbahn Gesellschaft) were the Länderbahnen. The DRG was founded in 1920, and subsumed the prior state railway systems. This German-language term is commonly used even in English-language works on railway history.
The Länderbahn period was more colorful than the periods that followed it (which could be said to be the general pattern of things in most nations). Locomotives were commonly painted in colorful, elaborately lined-out liveries, including greens, blues, sky blue, and many others. The DRG period that followed painted every locomotive in black with red wheels and frame, every passenger car in dark green and every freight car in oxide red/brown.
To model railway manufacturers and to some extent railfans this period is known as Epoch I.