The Undifferentiated Plains on Titan are vast expanses of terrains that appear radar-dark and fairly uniform in Cassini Synthetic Aperture Radar (SAR) images and are often referred to as “blandlands”. While the interpretation of several other geologic units on Titan - such as dunes, lakes, and well-preserved impact craters - has been relatively straightforward, the origin of the Undifferentiated Plains has remained elusive. SAR images show that these terrains are mostly found at mid-latitudes and show no major topographic features. Their gradational boundaries and paucity of recognizable features make geologic interpretation challenging. We mapped the distribution of these terrains using SAR swaths up to flyby T92 (7/2013), which cover > 50% of Titan’s surface. We compared SAR images with other data sets, including topography, the response from RADAR radiometry, hyperspectral imaging data from Cassini’s Visual and Infrared Mapping Spectrometer (VIMS), and near infrared imaging from the Imaging Science Subsystem. We examined and evaluated different formation mechanisms, including (i) cryovolcanic origin, consisting of overlapping flows of low relief or (ii) sedimentary origins, resulting from fluvial/lacustrine or aeolian deposition, or accumulation of photolysis products created in the atmosphere. Our results are consistent with a sedimentary origin for the Undifferentiated Plains. We discuss the possible contributing processes (photolysis products, aeolian, and fluvial/lacustrine deposition). VIMS and radiometry analysis of the Undifferentiated Plains presented here is consistent with tholin-like materials as a major component for the materials in the Plains. We conclude that the Undifferentiated Plains are sedimentary in origin and likely formed by a combination of aeolian, fluvial and lacustrine deposition, together with atmospheric organic particle deposition, possibly in differing proportions depending on location.