On the Bristol mapping portal, identify the earliest historical map available in the 'Historic basemaps' section. Also, find the map legend and list the three local authorities that share a border with Bristol. State the name of the oldest map and the three neighboring authorities.
Navigate to maps.bristol.gov.uk. Click on 'Browse historic basemaps' to expand the list of historical maps. Identify the map with the earliest year from the displayed list. Click on the 'Legend' link. Locate the 'Neighbouring authorities' section within the legend. Extract the names of the three neighbouring authorities listed. State the name of the oldest map and the three neighbouring authorities.
The oldest map identified is '1750 Rocque'. The three neighbouring authorities listed are 'Bath and North East Somerset', 'North Somerset', and 'South Gloucestershire'. The final answer accurately states both the oldest map and the three neighbouring authorities.