[Acko]

The map itself is a collection of bitmap files. The history files (countries on the map) are plain text documents containing stuff like who owns the province, controller, cores (representing claims, revanchism), province culture, etc. 
Example of a typical province history file:

Code:

# 183 Île-de-France - Principal cities: Paris

owner = FRA
controller = FRA
capital = "Paris"
citysize = 70000
culture = cosmopolitan_french
religion = catholic
hre = no
cot = yes
base_tax = 12
trade_goods = grain # gameplay, see EU II
manpower = 8
add_core = FRA
discovered_by = eastern
discovered_by = western
discovered_by = muslim
discovered_by = ottoman
courthouse = yes # Exception: Le Parlement de Paris
fort1 = yes
fort2 = yes
marketplace = yes
temple = yes # La Notre Dame de Paris
university = yes # La Sorbonne

1399.1.1  = { add_core = ENG } # To simulate the hundred years war
1420.1.1   = { controller = ENG } # Captured by the English
1437.1.1   = { controller = FRA } # Retaken by Charles VII
1475.8.29  = { remove_core = ENG } # Treaty of Picquigny
1500.1.1   = { citysize = 100000 constable = yes }
1550.1.1   = { citysize = 130000 regimental_camp = yes } #customs_house = yes
1571.1.1   = { revolt_risk = 5 } # Unrest spreads in catholic territory: massacres of protestants in Rouen, Orange & Paris
1573.8.23  = { revolt_risk = 10 } # Saint Barthelew's Day Massacre
1574.5.1   = { revolt_risk = 0 } # Charles IX dies, situation cools a bit    
1584.1.1   = { revolt_risk = 7 } # Situation heats up again, even Paris is restless
1588.1.1   = { revolt_risk = 10 } # Paris turns against the King and sides with the de Guises
1588.12.1  = { revolt_risk = 12 } # Henri de Guise assassinated at Blois, Ultra-Catholics into a frenzy
1589.1.1   = { base_tax = 14 } # At the Walls of Paris: French Wars of Religion
1590.1.1   = { fort3 = yes }
1594.1.1   = { revolt_risk = 8 } # 'Paris vaut bien une messe!', Henri converts to Catholicism
1598.4.13  = { revolt_risk = 3 } # Edict of Nantes, alot more freedom to the protestants
1598.5.2   = { revolt_risk = 0 } # Peace of Vervins, formal end to the Wars of Religion
1600.1.1   = { citysize = 220000 }
1604.1.1   = { war_college = yes } # Exception 'par excellence': La Prytanée Militaire Nationale
1621.1.1   = { base_tax = 15 } # Richelieu
1631.1.1   = { revolt_risk = 3 }
1633.1.1   = { revolt_risk = 0 }
1648.5.1   = { revolt_risk = 5 } # New tax levied by the Parliament of Paris, first Fronde coming up
1648.8.1   = { revolt_risk = 10 } # Cardinal Mazarin arrests the leaders of the Parliament, Paris rises up and barricades the streets
1648.10.21 = { revolt_risk = 0 revolt = { type = revolutionary_rebels size = 2 } controller = REB } # The First Fronde hits Paris, officials flee from the city
1649.3.1   = { revolt = {} controller = FRA } # Maréchal Condé besieges and takes back the city, little to no bloodshed - Peace of Rueil signed, peace returns, although Paris remains anti-cardinalist
1650.1.1   = { citysize = 430000 }
1650.1.14  = { revolt_risk = 7 } # Mazarin arrests the Princes Condé, Conti & Longueville, the beginning of the Second Fronde.
1651.4.1   = { controller = FRA revolt_risk = 4 } # An unstable peace is concluded
1651.12.1  = { revolt_risk = 7 } # Mazarin returns from exile, Condé sides with Spain, situation heats up again
1652.7.2   = { revolt = { type = revolutionary_rebels size = 1 } controller = REB revolt_risk = 3 } # The gates of Paris opened for Condé's troops
1652.10.21 = { revolt = {} controller = FRA revolt_risk = 0 } # The King is allowed to enter Paris again, Mazarin leaves France for good. Second Fronde over.
1665.1.1   = { workshop = yes tax_assessor = yes } # Colbert's reforms
1670.1.1   = { fort4 = yes }
1700.1.1   = { citysize = 510000 }
1725.1.1   = { fort5 = yes }
1750.1.1   = { citysize = 576000 }
1760.1.1   = { fort6 = yes }
1773.1.1   = { base_tax = 16 } # Turgot & the Economic Reforms
1789.7.4   = { revolt = { type = revolutionary_rebels size = 3 } controller = REB } # The storming of the Bastille

1789.7.14  = {    revolt = {}
        owner = RFR
        controller = RFR
        add_core = RFR
        remove_core = FRA
        fort5 = yes # these all vanish on owner change
        fort6 = yes
        war_college = yes
        tax_assessor = yes
         } # The storming of the Bastille
1800.1.1   = { citysize = 581000 }
1814.4.11  = {    owner = FRA
        controller = FRA
        add_core = FRA
        remove_core = RFR
        fort5 = yes
        fort6 = yes
        war_college = yes
        tax_assessor = yes
         } # Treaty of Fontainebleau, Napoleon abdicates unconditionally
1815.3.20  = {    owner = RFR
        controller = RFR
        add_core = RFR
        remove_core = FRA
        fort5 = yes
        fort6 = yes
        war_college = yes
        tax_assessor = yes
         } # Napoleon enters Paris
1815.7.8   = {    owner = FRA
        controller = FRA
        add_core = FRA
        remove_core = RFR
        fort5 = yes
        fort6 = yes
        war_college = yes
        tax_assessor = yes
         } # The French monarchy is restored

A breakdown of each property here:
Owner - The legal owner of the province. (here it is the tag FRA, or France)
Controller - Who controls the province. (Used to represent military occupation - A tag different from the owner will mean that somebody else is occupying the province.)
Capital - The province capital. (Used for aesthetic and for the population.)
Citysize - The population of the province capital. (Not much meaning here.)
Culture - The culture of the majority of the province's inhabitants. (self-explanatory.)
Religion - Majority religion in the province. (again, self-explanatory.)
HRE - If 'yes', the province is part of the Holy Roman Empire, which is an entirely new post in of itself.
COT - Not all provinces will have this, but if yes, the province is a center of trade. (This is where you send your merchants to trade.)
Manpower - How much the province contributes to the national manpower pool. (Needed for recruiting regiments and reinforcing existing ones).
Add core (add_core) - Adds a country's core to the province. (These are used to represent provinces that are considered part of a country's 'patrimony'. Countries can take core provinces that are not owned by them infamy-free in vanilla EU3.)