Question

Why were the citizens of Washington, DC, not allowed to vote in presidential elections until 1961?

Answer 1

Washington DC is not a US state - it's a district, which means it has no representation in the Congress or in the Electoral College. The lack of Electoral College representation was changed with the 23rd Amendment to the Constitution.

Explanation:
There are a couple of things to know:

The US Constitution, in Article 2, calls for states of the USA to determine, in their own way, how electors were to be selected (as part of the Electoral College). This language was modified in a few Amendments, starting with the 12th, that gives more guidance on the selection process.
(People don't vote directly for President. Instead, people vote for representatives, called Electors, who cast votes for President).

Washington DC is not a state - it's a district.
The District of Columbia, commonly known as Washington DC, is a bit of a strange place when it comes to government. It's the location of the seat of government for the USA, a country that has always prided itself on the ability of citizens to vote and exercise democracy. And yet, Washington DC has little governing authority of its own.

From its inception in 1802 until 1973, the government of DC was appointed by the President of the USA. In 1973, DC was given the ability to vote for a mayor and a council.

Hope this will help you.... ✌

Answer 2

Washington DC is a district i.e. DC stands for District of Columbia.  

As it was not a state, it had no representation in Electoral College or the Congress.

The matter was changed by the 23rd Amendment of the Constitution in 1961.

For this reason, the citizens of Washington, DC, were not allowed to vote in presidential elections until 1961.