The information was released by the Administration Office of the U.S. Federal Courts. There are 2,758 federal district judges.

The number of warrants they approved last year was released yesterday.

http://www.uscourts.gov/news/2018/06/28/2017-wiretap-report-orders-and-convictions-rise

The same office is responsible for releasing the number of Foreign Intelligence Surveillance Court (FISC) warrants.

http://www.uscourts.gov/sites/default/files/ao_foreign_int_surveillance_court_annual_report_2017.pdf

Judge Rosemary Collyer is pictured at the top of this post. She heads the FISA court.

http://www.fisc.uscourts.gov/about-foreign-intelligence-surveillance-court

The Office of the Director of National Intelligence (DNI) released a 41-page report in May called "Statistically Transparent Report Regarding Use of National Security Authorities for 2017."

https://www.dni.gov/index.php/newsroom/press-releases/item/1867-odni-releases-annual-intelligence-community-transparency-report

It provides statistics of the use of FISA warrants.

https://www.dni.gov/files/documents/icotr/2018-ASTR----CY2017----FINAL-for-Release-5.4.18.pdf