The legislation that disposed of the Northwest Territory after the Revolutionary War included a rectangular survey system known as:

The correct answer pertains to the rectangular survey system established by the legislation that governed the disposition of the Northwest Territory after the Revolutionary War. This survey system, also known as the Public Land Survey System (PLSS), was developed to systematically divide land into rectangles or sections to facilitate settlement and sale.

The significance of the rectangular survey system is that it provided a structured approach to land distribution, making it easier for settlers to understand the parcels available for purchase and use. The system divided land into townships and sections, allowing for an organized method of record-keeping and property ownership, which is essential for the establishment of land title and the foundation of property law in the United States.

In the context of the question, despite the choice listed as "leasehold mortgage subordinated to another leasehold mortgage" appearing again, this is incorrectly referenced. The focus should be on understanding the historical context and role of the rectangular survey system, which was integral to the development of the Northwest Territory.

The other options imply types of mortgages that do not directly relate to the legislative acts or survey methods used in the distribution of the Northwest Territory's lands. The emphasis of the question lies in the surveying technique that underpins the historical context rather than specific mortgage types. This illustrates the importance