Maximus Williamson Joins Phelps as Only 15-Year-Old Americans Under 4:20 in 400 IM

by Riley Overend 2

August 26th, 2022 International, National, News


Maximus Williamson elevated himself further into rarefied air at the 2022 Junior Pan Pacific Championships on Thursday, becoming the only 15-year-old American besides Michael Phelps to break 4:20 in the 400-meter IM. 

Sometimes it takes another generational talent to put Phelps’ greatness in perspective. Case in point: Williamson’s 4:17.58 is more than two seconds faster than any other 15-year-old American in history not named Phelps, but it’s still two seconds slower than the 4:15.20 that Phelps blazed back at the 2001 Spring Nationals.


  • Jr World: 4:10.02 – Ilia Borodin, RUS (2021)
  • Jr Pan Pac: 4:12.59 – Chase Kalisz (2012)


  1. Ei Kamikawabata, Japan – 4:15.23
  2. Maximus Williamson, USA – 4:17.58
  3. Riki Abe, Japan – 4:17.96

Williamson, who came into the race as the No. 6 seed, blew away the field on the backstroke leg before falling behind Ei Kamikawabata of Japan on the breaststroke leg. Williamson out-split Kamikawabata by more than a second on the freestyle anchor, but it wasn’t quite enough to complete the comeback. Williamson still picked up his second individual silver medal at the meet after posting a 1:48.21 in the 200 free on Wednesday, which made him the fastest 15-year-old American of all-time in the event.

Splits, Williamson vs. Kamikawabata

Maximus Williamson, Silver Ei Kamikawabata, Gold
100 Butterfly 58.67 57.88
100 Backstroke 1:04.19 1:06.40
100 Breaststroke 1:16.36 1:11.56
100 Freestyle 58.38 59.39
400 IM  4:17.58 4:15.23

Williamson shaved nearly three seconds off his previous best from April’s International Team Trials, where he placed second in the B-final with a 4:20.01. Before that, his previous best was a 4:27.53 from last July, meaning he’s dropped nearly 10 seconds in the past year. He was already the No. 2 performer nationally for his age, but now he’s created some separation from the pack. 

Fastest 15-Year-Old Americans Ever, 400 IM

  1. Michael Phelps – 4:15.20 (2001)
  2. Maximus Williamson – 4:17.58 (2022)
  3. Sean Grieshop – 4:20.25 (2014)
  4. Carson Foster – 4:21.10 (2017)
  5. Andrew Seliskar – 4:21.16 (2012)

Williamson’s new personal best not only makes him the second-fastest 15-year-old American of all-time, but also the fifth-fastest performer ever in the boys 15-16 national age group (NAG). Three of the top five times on each list were clocked at Junior Pan Pacs. 

Best 400 IM Performers, Boys 15-16 NAG

  1. Carson Foster – 4:14.73 (2018)
  2. Michael Phelps – 4:15.20 (2001)
  3. Sean Grieshop – 4:15.67 (2015)
  4. Gunnar Bentz – 4:17.43 (2012)
  5. Maximus Williamson – 4:17.58 (2022)
  6. Jake Foster – 2:19.40 (2017)
  7. Marci Barta – 4:19.47 (2016)
  8. Cooper Lucas – 4:19.95 (2021)
  9. Andrew Seliskar – 4:20.96 (2013)
  10. Jarod Arroyo – 4:20.96 (2017)

The other American in the A-final was 17-year-old  Cooper Lucas, Williamson’s new teammate at Lakeside Aquatic Club and Keller High School in Texas. Lucas placed sixth with a personal-best time of 4:19.77. 

In This Story

Leave a Reply

Notify of

oldest most voted
Inline Feedbacks
View all comments
Retired Swimmer
3 months ago

Such a badass name. Of course he’d be good at a badass event like the 400 IM.

Bill Price
3 months ago

I don’t have a comment, I just like his name.

About Riley Overend

Riley is an associate editor interested in the stories taking place outside of the pool just as much as the drama between the lane lines. A 2019 graduate of Boston College, he arrived at SwimSwam in April of 2022 after three years as a sports reporter and sports editor at newspapers …

Read More »