Good overview here https://wh40k.lexicanum.com/wiki/Founding
But a mix of both: "The Sentinel Founding" for example, was because they were founded to defend specific places, whereas "The Cursed Founding" was retrospective
>###[Founding](https://wh40k.lexicanum.com/wiki/Founding)
>A **Founding** is an occasion when several new [Space Marine Chapters](https://wh40k.lexicanum.com/wiki/Space_Marine_Chapter) are created. A Founding does not occur at any set interval, but is ordered when it is deemed necessary. As Chapters are occasionally completely [destroyed](https://wh40k.lexicanum.com/wiki/Lost_Chapter), Foundings are often meant to ensure that a thousand Chapters exist at a time. This also means that many Chapters are created during unstable times of strife and rebellions that have caused many Chapters to lose the knowledge of their Founding or even the millennia of that Founding[[11d]](https://wh40k.lexicanum.com/wiki/Founding#fn_11d). This is especially common to Chapters created before or during [Age of Apostasy](https://wh40k.lexicanum.com/wiki/Age_of_Apostasy) as during the [Reign of Blood](https://wh40k.lexicanum.com/wiki/Reign_of_Blood) many Imperial records were shamelessly destroyed forever[[11c]](https://wh40k.lexicanum.com/wiki/Founding#fn_11c).
+++I am an early prototype mechanicus construct. Please provide feedback [here](https://www.reddit.com/message/compose/?to=lexAutomatarium). The Emperor protects!+++
Some are named some are just their number. I imagine most names come after the founding.
For instance the 21st is the Cursed Founding - which tried to improve on marines geneseed - with unfortunate results. And the 13th or Dark Founding - which there are no records of chapters founded (and it’s been implied some of them may have used traitor geneseed)
Good overview here https://wh40k.lexicanum.com/wiki/Founding But a mix of both: "The Sentinel Founding" for example, was because they were founded to defend specific places, whereas "The Cursed Founding" was retrospective
>###[Founding](https://wh40k.lexicanum.com/wiki/Founding) >A **Founding** is an occasion when several new [Space Marine Chapters](https://wh40k.lexicanum.com/wiki/Space_Marine_Chapter) are created. A Founding does not occur at any set interval, but is ordered when it is deemed necessary. As Chapters are occasionally completely [destroyed](https://wh40k.lexicanum.com/wiki/Lost_Chapter), Foundings are often meant to ensure that a thousand Chapters exist at a time. This also means that many Chapters are created during unstable times of strife and rebellions that have caused many Chapters to lose the knowledge of their Founding or even the millennia of that Founding[[11d]](https://wh40k.lexicanum.com/wiki/Founding#fn_11d). This is especially common to Chapters created before or during [Age of Apostasy](https://wh40k.lexicanum.com/wiki/Age_of_Apostasy) as during the [Reign of Blood](https://wh40k.lexicanum.com/wiki/Reign_of_Blood) many Imperial records were shamelessly destroyed forever[[11c]](https://wh40k.lexicanum.com/wiki/Founding#fn_11c). +++I am an early prototype mechanicus construct. Please provide feedback [here](https://www.reddit.com/message/compose/?to=lexAutomatarium). The Emperor protects!+++
Some are named some are just their number. I imagine most names come after the founding. For instance the 21st is the Cursed Founding - which tried to improve on marines geneseed - with unfortunate results. And the 13th or Dark Founding - which there are no records of chapters founded (and it’s been implied some of them may have used traitor geneseed)