The easily readable structure of having an `if` keyword which controls execution of a following block of code is so prevalent in programming that it seems to just be part of it.

However, programming started out with machine code that was far away from the easy to understand

```
if condition
    do thing
```

What was the first time a programmer was able to use this simple and intuitive way of executing code based on a condition?

This excludes `IF...GOTO` statements, as that - in the sense of this question - only allows to execute a `GOTO` statement, opposed to arbitrary code. Also condition and code to execute are split up there and not together anymore. This is more about the "usability for programmers" perspective than about the technical ability to support this feature.

As user Raffzahn mentioned, this can be called "_the first (block) structured language_".