The northern border of modern-day Louisiana mainly follows the state line between Louisiana and Arkansas, while the northern border of the Territory of Orleans (established in 1804) was defined by different geographic and political boundaries at that time.
In the early 19th century, the Territory of Orleans was part of the larger land acquired in the Louisiana Purchase from France in 1803. The territory's borders were determined based on both geographical landmarks and existing political boundaries. The northern border of the Territory of Orleans primarily corresponded to the southern boundary of the state of Arkansas, which was created later.
Overall, while the modern northern border of Louisiana aligns closely with the historic northern boundary of the Territory of Orleans, exact delineations of boundaries may differ slightly based on surveying practices and evolving political governance over time. Today, the northern border is a well-defined political boundary, whereas historical borders were more fluid and subject to interpretation.