There are many features of the Underground Railroad that can best be understood by means of a geographical representation of the system. Such a representation it has been possible to make by piecing together the scraps of information in regard to various routes and parts of routes gathered from the reminiscences of a large number of abolitionists. The more or less limited area in which each agent operated was the field within which he was not only willing, but was usually anxious, to confine his knowledge of underground activities. Ignorance of one's accomplices beyond a few adjoining stations was naturally felt to be a safeguard. The local character of the information resulting from such precautions places the investigator under the necessity of patiently studying his materials for what may be called the cumulative evidence in regard to the geography of the system. It is because the evidence gathered has been cumulative and corroborative that a general map can be prepared. But a map thus constructed cannot, of course, be considered complete, for it cannot be supposed that after the lapse of a generation representatives of all the important lines and branches could be discovered. Nevertheless, however much the map may fall short of showing the system in its completeness, it will be found to help the reader materially in his attempt to realize the extent and importance of this movement. The underground system, in accordance with the statement of James Freeman Clarke, is commonly understood to have extended from Kentucky and Virginia across Ohio, and from Maryland through Pennsylvania, New York and New England to Canada.[346] But this description is inadequate, for it fails to include the states west of Ohio. Henry Wilson extends the field westward by asserting that the "territory embraced by the Middle States and all the Western States east of the Mississippi ... was dotted over with 'stations,'" and "covered with a network of imaginary routes, not found ... in the railway guides or on the railway maps;"[347] and in another place he quotes the Rev. Asa Turner, a home missionary, who went to Illinois in 1830, who says: "Lines were formed through Iowa and Illinois, and passengers were carried from station to station ... till they reached the Canada line."[348] The association of Kansas with the two states just named as a channel for the escape of runaways from the southwestern slave section, is made by Mr. Richard J. Hinton.[349] The addition of one other state, New Jersey, is necessary to complete the list of Northern states involved in the Underground Railroad system.[350] This region, which forms nearly one quarter of the present area of the Union, constituted the irregular zone of free soil intervening between Southern slavery and Canadian liberty. [346] _Anti-Slavery Days_, p. 81; M. G. McDougall, _Fugitive Slaves_, p. 61. [347] _Rise and Fall of the Slave Power in America_, Vol. II, p. 66. [348] _Ibid._, p. 68.