| RHP1219 | Plan of the lands of Brims, Thurso, Caithness | 1769 |
| RHP1222/1 | Plan of proposed harbour at Crosskirk, Thurso, Caithness | 1840 |
| RHP1222/2 | Sections of pier at Crosskirk Harbour, Thurso, Caithness | 1840 |
| RHP1223 | Plan of the estate of Forss the property of James Sinclair | 1800 |
| RHP1224/1-4 | Plans of the farms of Baillie and Westfield, Caithness | 1828 |
| RHP1680 | Plan of intended harbour near Holburn Head or Scrabster Roads, Caithness | 1840 |
| RHP1682 | Plan of Thurso bay showing situations of salmon nets, Caithness | 1852 |
| RHP1731 | Plan of Scrabster Harbour taken from parliamentary plan, Caithness | 1862 |
| RHP1732 | Architectural drawing of cottages to be erected at Scrabster, Thurso, Caithness | 6 Dec 1860 |
| RHP2790 | Ordnance Survey 1/2500 plan (Caithness, IV.7), marked to show boundary between the Forss fishings and those belonging to the crown | 1906 |
| RHP2791 | Plan of the lands of Scrabster | 1831-1837 |
| RHP2792 | Plan of the lands of Scrabster | 1848 |
| RHP2793 | Plan of lands of Lythmore, with annotations regarding quality and use of land | 18th century |
| RHP2794 | Plan of the lands of Lythmore | 1831-1837 |
| RHP2795 | Plan of the lands of Lythmore, Thurso, Caithness | 1848 |
| RHP2796 | Plan of the lands of Lythmore, Thurso, Caithness | 1848 |
| RHP2797 | Plan of aqueduct from the south end of Loch Calder to Thurso, prepared in connection with deed of wayleave to Thurso Police Commissioners. | 1876 |
| RHP2951 | Plan of Forss Common | 1834 |
| RHP3907 | Plan of Forss Common | 1831 |
| RHP3908 | Plan of the old town of Thurso and areas of the feus therein | 1833 |
| RHP4418 | Plan of the Forss estates, Caithness | 1919 |
| RHP4418/1 | Plan of the Forss estates, Caithness | 1919 |
| RHP4418/2 | Plan of the Forss estates, Caithness | 1919 |
| RHP4418/3 | Plans of the Forss estates, Caithness | 1919 |
| RHP5243 | Ordnance Survey 1/2500 plan (Caithness-shire Sheet V.6), marked to show proposed extended harbour at Scrabster | 1891 |
| RHP5441 | Bound plans and sections of proposed work at Scrabster harbour. | 1955 |
| RHP6153/1 | Plan of the division of the Commonty of the Hill of Forss, Thurso, Caithness | 1833 |
| RHP6153/2 | Explanation of a plan of the Commonty of the Hill of Forss | 1831 |
| RHP6153/3 | Plan and section of slate quarry near Wass (bound in report thereon) | 1832 |
| RHP6153/4 | Plan of bed of marle in the Moss of Geise | 1832 |
| RHP6322 | Ordnance Survey 1/2500 plan [Caithness, V. 14], | c. 1872 |
| RHP6329 | Ordnance Survey 6 inch plan (Caithness, sheets V and XI combined) | c. 1876 |
| RHP6331 | Ordnance Survey 1/2500 sheet (Caithness, V. 14 and XI.2 combined) | c. 1872 |
| RHP6335 | Ordnance Survey 1/2500 plan (Caithness, V. 11 and 15 combined) | Late 19th century |
| RHP6363/1 | Ordnance Survey 1/2500, Thurso | c 1872 |
| RHP6363/2 | Ordnance Survey 1/2500, Millbank and South of Thurso | c 1872 |
| RHP8720 | Plan of Thurso Bay from the point of Holborn Head to Clardon Head and the coast to Castlehill (Vignettes of sailing vessels) (1-2) | 1789 |
| RHP11465 | Architectural plan of property belonging to a solicitor at the corner of Caithness Street and Brabster Street in Thurso | 1882 |
| RHP11609 | Plan of intended road from the Kirk of Farr to the town of Thurso. | 1797 |
| RHP11610 | Plan of intended road from the town of Thurso to Dunbeath, Caithness | 1797 |
| RHP11612 | Plan of intended road from Huna (Houna) Inn to the town of Thurso. | 1798 |
| RHP11663 | Plan of two roads from Drum Hollistan to Thurso. | 1809 |
| RHP11664 | Plan of intended road from Dunbeath to Thurso. | 1809 |
| RHP11692 | Plan of road from the town of Thurso to Halkirk and Achcomhaire (Achorlie). | 1805 |
| RHP12277 | Plan of the farm of Mains Of Brims | 1867 |
| RHP13144 | Sketch plan of Scrabster Harbour: 1891. | 1891 |
| RHP13149 | Plan of Thurso River Harbour, Caithness | 1891 |
| RHP17447 | Ordnance Survey 1/2500 plan marked to show proposed branch of the [Highland Railway] from Thurso to Scrabster. | Late 19th century |
| RHP18201 | Plan of the Sutherland and Caithness Railway from Thurso to Georgemas Junction. | 1871 |
| RHP22355 | Plan showing line of old and new dykes on Mr. Ferryman's property at Meeting House Lane, Thurso: [post 1870]. | 1870 |
| RHP22357 | Copy plan of the sub-division of the lot of commons in the Hill of Forss allotted to the feuars of the town of Thurso | c 1833 |
| RHP30910 | Volume containing 7 architectural plans of Thurso Combination Poorhouse. | 1854-1912 |
| RHP32970 | Plan of Forss Common. | 1831 |
| RHP38311/5 | L.M.S. Railway, Northern Section: Gradient profiles, stations etc | 1937 |
| RHP43417 | Ordnance Survey 1 inch map marked to show parish boundaries and quoad sacra parish of Shurrey. | 1902 |
| RHP43572 | Plan of Forss Common, marked to show division. | 1831 |
| RHP43589 | Plan, sections and elevation of proposed harbour at Scrabster. | 1839 |
| RHP43590 | 1. Plan and section of intended harbour and road thereto at Scrabster. 2. Book of reference | 1840 |
| RHP43594 | 1. Plan and sections of proposed improvements at Thurso River Harbour. 2. Book of reference 3. Gazette notice 4-6. Duplicates of 1-3 | 1877 |
| RHP43596 | 1. Bound plans and sections of proposed works at Thurso River Harbour. 2. Book of reference 3. Thurso River Harbour Act, 1889 4-5. Duplicates of nos 1-2 | 1889 |
| RHP43597 | Bound plans and sections (with gazette notice bound in) of proposed works at Scrabster Harbour. | 1897 |
| RHP43597/1 | Bound plans and sections (with gazette notice bound in) of proposed works at Scrabster Harbour | 1897 |
| RHP43597/2 | Provisional order for proposed works at Scrabster Harbour | 1897 |
| RHP43597/3 | Order for proposed works at Scrabster Harbour | 1897 |
| RHP43641 | Ordnance Survey 1/2500 plan (Caithness sheet V.ll) marked to show proposed improvements at Thurso River Harbour. | 1877 |
| RHP43646 | Plan of Forss estates showing division into lots, including subjects in Scrabster. | 1919 |
| RHP43650 | Plan, sections and elevations of proposed apron wall at Scabster Harbour. | 1922 |
| RHP43655 | Plan of lands of Murkle, with numbered divisions. | [20th century] |
| RHP43668 | Ordnance Survey 1/2500 plan marked to show proposed enlargement of holding on farm of Mains of Forss. | 1913 |
| RHP43671 | Ordnance Survey 6 inch plan marked to show proposed new and enlarged holdings and acreage of arable land and pasture on these, on farms of Broynach and Mayfield. | 1913 |
| RHP46216 | 1. Plan of Forss Common 2. Duplicate of no. 1 | 1831 |
| RHP49640 | Plan and section of line of tramway from Oldfield towards Thurso Castle, Caithness | 1880 |
| RHP78982 | Ordnance Survey 6 inch plan (Caithness, sheet XI) marked to show farm boundaries | [1944-1955] |
| RHP78983 | Ordnance Survey 6 inch plan (Caithness, sheet XII) marked to show farm boundaries | [1944-1955] |
| RHP79523 | Ordnance Survey 6 inch plan (Caithness, sheet IV) | [post 1907] |
| RHP79524 | Ordnance Survey 6 inch plan (Caithness, sheet V) marked to show farm boundaries: [1944 x 1954] | nd |
| RHP79525 | Ordnance Survey 6 inch plan (Caithness, sheet VI) marked to show farm boundaries: [1944 x 1954] | nd |
| RHP79529 | Ordnance Survey 6 inch plan (Caithness, sheet X) marked to show farm boundaries: [1944 x 1954] | nd |
| RHP81733 | Plan (from Ordnance Survey) showing boundaries at Thurso Station (British Railways) | 1969 |
| RHP81757 | Plan, elevation, section and details of overbridge no. 5 between Hoy and Thurso (British Railways) | [c 1948] |
| RHP93953/57 | General plan of Scrabster Harbour | Jan 1950 |
| RHP93953/64 | General plan of Thurso River Harbour | Jan 1955 |
| RHP94038 | Plan of disputed ground between High (Main) Street and Cowgate, Thurso, showing site of `Old Meeting House', produced in causa Stewart v Grant | Dec 1823 |
| RHP94251 | Plan of Thurso Freight Sundries Depot (British Railways) | [1969] |
| RHP97559 | Ordnance Survey 6 inch plan (Caithness, sheet IV) coloured and marked to show classification of land | [1944-1954] |
| RHP97560 | Ordnance Survey 6 inch plan (Caithness, sheet V) coloured to show classification of land | [1944-1954] |
| RHP97562 | Ordnance Survey 6 inch plan (Caithness, sheet X) coloured and marked to show classification of land | [1944-1954] |
| RHP124373 | Plan of Air Ministry Fuel Depot Sidings at Hoy, London Midland & Scottish Railway, Caithness | c 1940 |
| RHP140018 | Plan of area between the Bishop's Castle at Scrabster and the town of Thurso | [1832] |
| RHP141252 | Architectural drawing of shop premises in Traill Street, Thurso | 16 Sep 1847 |
| RHP142365 | Plans of proposed extension of Thurso burgh boundaries, Caithness | 1957 |
| RHP142365/1 | Plan of proposed extension of Thurso burgh boundaries | 28 Mar 1957 |
| RHP142365/2 | Plan of proposed extension of Thurso burgh boundaries | 9 May 1957 |
| RHP142365/3 | Thurso burgh development plan | 1 Jul 1957 |
| RHP142365/4 | Thurso burgh development plan | 1 Jul 1957 |
| RHP142365/5 | Thurso burgh development plan: written statement | 1957 |
| RHP142365/6 | Thurso burgh development plan | 1 Jul 1957 |
| RHP142365/7 | Thurso burgh development plan | 1 Jul 1957 |
| RHP142365/8 | Thurso burgh development plan | 1 Jul 1957 |
| RHP142661 | Plan of Glengolly corner on the Thurso - Glengolly - Halkirk road, Caithness | 9 Jul 1978 |
| RHP142765 | Ordnance Survey 6 inch plan (Caithness, sheet [-]) | c 1910 |
| RHP142768 | Ordnance Survey 1 inch plan (Reay, sheet [-]; Wick, sheet 116) | c 1910-c 1924 |
| RHP142770 | Ordnance Survey 6 inch plan (Caithness, sheet V) | c 1910-c 1956 |
| RHP142771 | Plan of cottages at Scrabster, Caithness | c 1900 |
| RHP142811 | Plans of Scotscalder estate, Caithness | c 1907 |
| RHP142811/1 | Ordnance Survey 6 inch plan (Caithness sheet XI) | c 1907 |
| RHP142812 | Plans of Lythmore estate, Caithness | c 1906 |
| RHP142812/1 | Ordnance Survey 1 inch map (Caithness sheet IV.16) | c 1906 |
| RHP142812/2 | Ordnance Survey 1 inch map (Caithness sheet V.13) | c 1906 |
| RHP142812/3 | Ordnance Survey 1 inch map (Caithness sheet X.4) | c 1906 |
| RHP142812/4 | Ordnance Survey 1 inch map (Caithness sheet XI.I) | c 1906 |
| RHP143000/3/28 | Ordnance Survey 1 inch map (Sheet 115, [Reay]) | 1878 |
| RHP143353 | Copy plan of Holburn Head, Thurso | 1796 |
| RHP160000/32/93 | Plan of shootings at Lybster, Kennachy, Upper Dounreay, Skiall, Hallam, Dalclaggie and Stemster, Caithness (Dounreay Scheme) | 22 Feb 1978 |