Until 1866
Until 1866, the Principality of Andorra had no official
flag, but used frequently a sign, (mixing a medevial
Catalan and House of Foix), generally vertical stripes
(sometimes in large horitzontales). Various sources
mention it as flag of country, but no official document
to prove it. Some documents indicate that Napoleon might
have given these colors in 1806.

From 1866, a flag (mixing French and Catalan flags colors)
was officially established. According Aufrere, Napolon
III gave it to the Co-Principality.
From 1866 until 1931
The vertical version is sometimes presented with a badge
which featured some variation depending on the place
of manufacture (Catalonia or France).
Variations of the flag of the Principality
depending of the place of manufacture.
From 1931 until 1939
During this period, the flag was used indifferently
with or without central shield and the colors horizontally
or vertically.
During the reign of Boris I (Boris Skossyreff)
July 6, 1934: Baron Boris Skossyreff, who had fled Russia
in 1917, and after traveling in many countries, arrived
in Andorra where he had intended to proclaim himself
king. (He had previously stayed in Andorra).
He obtained the support of a member of the General Council,
Pere Riba Torres, who managed to get support from the
rest of the House (with the exception of a Councillor).
Boris promised freedoms and modernization of the country
(at the time very isolated and poor) and money afloat
thanks to the establishment of a tax haven and foreign
investment.
July 8, 1934: The General Council voted for the
monarchy proposed by Boris Skossyreff, who proclaimed
himself king and representative of the Crown of France
(the duke), who took the opportunity to claim before
the courts jurisdiction over Andorra corresponding
to the French monarchy. (A law enacted by Napoleon
had given the French state in 1806.)
July 8, 1934: Councilor Cinto opposition, (the only
one of 24 Councillors), moving to the Bishop of Palai
La Seu d'Urgell (one of the co-princes of Andorra),
to explain the situaion. France, for its part, gave
up to intervene, accepted the decision of the General
Council of Andorra.
July 9, 1934: A provisional government was formed.
The General Council was converted into Parliament,
and announced the future drafting of a constitution.
The absolute freedom of political, religious and printing
was proclaimed.
July 10, 1934: Parliament revote confidence in the
monarchy (23 votes to 1), and popular support seems
absolute.
July 14, 1934: A group of Spanish Civil Guard was
sent by the bishop of La Seu d'Urgell, and sent Boris
first detained. He was then moved to Barcelona and
Madrid, and finally deported to Portugal.
From 1939 until 1993
The tricolor with vertical stripes continued to be seen
occasionally without shield, but from this period, it
became customary to use the version with it to differentiate
the national flag from those of Chad and Romania.
From 1993
With the votation of the Constitution in 1993)
and with the entry in the United Nations organisation
(1994), the official flag was formalized (in 1996):
Verical with the bands and the shield in the center
of the country.