The goal of ever closer union appears in both the Maastricht Treaty and the Treaty of Rome.

https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL...

>RESOLVED to continue the process of creating an ever closer union among the peoples of Europe, in which decisions are taken as closely as possible to the citizen in accordance with the principle of subsidiarity,

Now you might say, ah! This text also says that decisions must be taken as closely as possible to the citizens. Yes, the treaties do say that, the EU just doesn't do it. Of course it makes no sense, the claim about subsidiarity is in direct contradiction to the first part of the sentence, you can't be both in an ever-tightening political union and also have decisions made by local governments. In practice the first part is chased and the second part is ignored. EU decisions are taken in Brussels - far away from the average citizen - even about many issues that don't need to be decided there.

If you want to understand the real origins of the EU and where it's going, you need to read the Ventotene Manifesto. Written during WW2 by a group of imprisoned Italian communists led by Altiero Spinelli, it calls explicitly for a communist revolution that would unite all of Europe. Spinelli's document can be found here:

https://federalists.eu/federalist-library/the-ventotene-mani...

It says things like, "In order to respond to our needs, the European revolution must be socialist" and "By this dictatorship of the revolutionary party a new State will be formed, and around this State new, genuine democracy will grow". It goes on like that in quite some detail.

Although the document is insane Spinelli went on to be one of the founding architects of the EU. He is officially credited as a "pioneer of the EU":

https://european-union.europa.eu/principles-countries-histor...

and a "founding father of the EU":

https://en.wikipedia.org/wiki/Founding_fathers_of_the_Europe...

He became one of the first members of the European Commission and was a member of the European Parliament. He was also one of the primary authors of the "Draft Treaty for establishment of the European Union" in 1984 that directly led to the creation of the modern EU itself via the Maastricht Treaty, which imported a lot of its ideas. The Draft Treaty can be found here:

https://federalists.eu/federalist-library/draft-treaty-estab...

It not only mentions the goal of ever closer union (with no mention of subsidiarity), but mandates it legally in Article 11, which defines "cooperation" to mean control by member states and "common action" to mean things directly controlled by the EU institutions. It then states in plain English that a topic may be moved from cooperation to common action, but never in reverse. It also states that powers go through this one way transfer to the EU based only on a vote of the EU Parliament, with member state parliaments themselves getting no say in it.

So the idea of abolishing national states has always been very visible among the EU's "founding fathers".