REST API to create Stellar account?
There is no REST endpoint to create an account. An account is implicitly created after receiving at least 20 lumens. 

To create an account: 


Generate a private/public keypair. You can use the Stellar Laboratory Account Creator for that. 
Get at least 20 lumens, either from an exchange or through another account, sent to the public key you just created. 


That's it.

Official guide : https://www.stellar.org/developers/guides/get-started/create-account.html