by @Chris
How Gelderland took shape. The story starts on the Roman Rhine frontier, with the Franks, Frisians and Saxons and the Frankish gouwen. A small county named after Geldern on the Niers grew north across the Rhine: Zutphen (c. 1138), the Veluwe (1182) and Nijmegen (1247–48) made the Duchy of Guelders and its four quarters. Charles of Egmond held out against Burgundy and Habsburg and for a time ruled Groningen, Drenthe, much of Friesland and Utrecht, while his marshal Maarten van Rossum sacked The Hague (1528) and marched on Antwerp and Leuven (1542). In 1543 Guelders passed to Charles V. The Revolt split it: the three lower quarters became a province of the Dutch Republic, Upper Guelders stayed Spanish and was divided in 1713, and Geldern itself is German today. The Disaster Year 1672, the French period, the border treaty with Prussia (1816–17), the battles of 1944–45, Elten (1949–63) and the 1986 border change at Asperen bring it to the present province. Borders are built from the municipalities of 1812 (modern municipalities in Germany and Belgium), so they are accurate to a few kilometres; neighbouring states are drawn coarsely, and early medieval borders are reconstructions. Shades of green are Guelders; a golden tint marks Burgundian or Habsburg rule over the whole duchy. Sources: NLGis municipal borders 1812–1997 (O.W.A. Boonstra, DANS, CC0); © GeoBasis-DE / BKG (VG250); Statbel/geoBoundaries; A. Schoemaker, Gelre en zijn grenzen (historischetopografie.nl); G.H.A. Venner, De overheidsinstellingen van Spaans en Oostenrijks Gelre; Neue Deutsche Biographie (Geldern, Grafen und Herzöge); M. Witteveen, Maarten van Rossem; Wikipedia (nl, de, en) articles on the quarters, ambten, towns, sieges and treaties; preliminary research by @Chris.
Roman Empire · Batavians (allies inside the Empire) · Free Germania (Frisii, Chamavi, Bructeri …) · Franks · Saxons · Hamaland · Veluwe (gouw) · Betuwe (gouw) · Teisterbant · Duffelgouw · Hettergouw · Maasgouw · Mühlgau · Texandria · Salland · Twente · Drenthe (gouw) · Flethetti · Nifterlake · Frisians → Frisian lands (Friesland, Groningen) · County of East Frisia · Saxon Friesland (1498–1515) · County of Flanders · County of Holland (and Zeeland) · Prince-Bishopric of Utrecht · Duchy of Brabant · Duchy of Limburg · Lordship of Heinsberg · Prince-Bishopric of Liège · Electorate of Cologne · Prince-Bishopric of Münster · Principality of Salm (1802–1810) · Duchy of Jülich (and Berg) · Cleves (Brandenburg-Prussian from 1614) · Grand Duchy of Berg (1806–1813) · Burgundian → Habsburg → Spanish → Austrian Netherlands · France · Dutch Republic → Batavian Republic → Kingdom of the Netherlands · Belgium · Prussia → Germany · Prussian Upper Guelders (Geldern) · States' Upper Guelders (Venlo) · German occupation (1940–45) · Lordships inside Guelders (Culemborg, Buren, Bergh, Borculo …) · Charles of Guelders' conquests (Groningen, Drenthe, Friesland, Utrecht) · Guelders: Upper Quarter (Roermond, Venlo, Geldern) → Spanish, Austrian Guelders · Guelders: County of Zutphen · Guelders: Veluwe (Quarter of Arnhem) · Guelders: Quarter of Nijmegen (Rijk, Betuwe, Maas en Waal, Bommelerwaard) · Gelderland (department → province) · Army of Maarten van Rossum