Assam State Archives has a sizable collection of very rare and old maps such as:

Political map of Assam and adjoining countries
Different forest maps of Assam
Revenue maps
Geological maps
Different circle maps of Assam and Eastern Bengal covering the period of 1853 to 1948.

Illustrative List of Maps: 
MAP of Assam:

Part of District Lakhimpur Seasons 1807 to 71 & 1908-09
Revenue Survey District Luckimpoor, Seasons 1866 to 70
Revenue Survey District Nowgong, Surveyed in 1870-71
Survey District Cachar, Seasons 1878-82
Forest Survey Assam Circle, Nowgong District, Season 1904-05
Gauhati Circle District Kamrup, Seasons 1910-13, 1884-1897
Golaghat Circle District Sibsagar, Seaspon 1914-16, 1888-99
Lakhimpur District & Sadiya Frontier Tract, Seasons 1916-17, 1923-24
Cachar and Nowgong Districts, Seasons 1921-23
Garo Hills,Goalpara & Khasi & Jaintia Hills Districts, Season 1926-27
Lushai Hills District, Surveyed 1934-35
Palasbari Thana, District Kamrup, Season 1938
Tribal Boundaries Assam (Provisional) 1946
Boundary between The Khasi Hills & Kamrup, Season 1876-77

MAP of Assam & Burma:  

Lushai Hills, Pakokku & Upper Chindwin Districts, Chin Hills & Un-administered Area. Seasons 1853 to 1907-08
Lakhimpur District & Sadiya Frontier Tract , Tribal Area, Season 1925-26

MAP of The Province of Assam: under the jurisdiction of the Chief Commissioner, 1875  MAP of Burma and Andaman Island: 1889  MAP of Eastern Bengal & Assam: Parts of Districts Mymensingh & Sylhet, Season 1907-08  MAP of Assam & Bengal: Sylhet District, Tripura State, Season 1931-32