Top Series B companies in the United States

Companies that have closed a Series B - proven scaling motion, hiring aggressively. Filtered to companies headquartered in the United States.

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Ranked by current headcount across Series B companies headquartered in the United States. Refreshed daily.

1
Railway· San Francisco, California, United States
Railway’s mission is to build the cloud computing stack that unburdens you, so you can focus more on what matters to you.
- Series B
- 11.2k employees
- Founded 2020
2
Chief· New York, New York, United States
Chief is a community of ambitious women executives shaping the new era of leadership.Chief exists to create more possibilities for women’s power.Today’s leaders face seismic shifts unlike any generation before them. But they don’t have to do it alone. Networking is not just a necessity, it’s a door to unique possibilities. Our members catalyze their ambition with the tools, the network, and the space to do business, create change, and lead on. We believe that women are as ambitious as ever.We believe that leadership today is non-linear.We believe that connections between powerful women unlock possibilities. We believe that multihyphenate women are rewriting the rules of leadership for the next generation. Our strength lies in our diversity. Each new perspective grows our collective power.Chief is the only membership network that combines access to exclusive Clubhouses, world-renowned Guides and Executive Coaches, top-level training from the Wharton School of Business, annual summits, and events at the industry conferences that matter.Apply today: chief.com/apply
- Series B
- 7.6k employees
- Founded 2019
3
Datavant· New York, New York, United States
Datavant is the data collaboration platform trusted for healthcare. With a mission to make the world’s health data secure, accessible, and actionable, Datavant works with payers, providers, life sciences, legal and insurance clients globally to accelerate insights. Datavant enables more than 60 million healthcare records to move between thousands of organizations across the healthcare ecosystem, more than 80,000 hospitals and clinics, 75% of the 100 largest health systems, and 350+ real-world data partners. Datavant has office locations in Boston, New York and San Diego, with international offices in Barcelona and Galway. To learn more about Datavant, visit datavant.com and follow us on LinkedIn.
- Series B
- 7.3k employees
- Founded 2014
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4
GitHub· San Francisco, California, United States
As the global home for all developers, GitHub is the complete AI-powered developer platform to build, scale, and deliver secure software. Over 100 million people, including developers from 90 of the Fortune 100 companies, use GitHub to build amazing things together across 330+ million repositories. With all the collaborative features of GitHub, it has never been easier for individuals and teams to write faster, better code.
- Series B
- 6.7k employees
- Founded 2008
5
Outlier AI· Oakland, California, United States
Outlier shut down in 2022, this page remains as a memory of our company and on the resumes of our team.Business intelligence is ready for a change. We don't believe the world needs any more dashboards, charts or data warehouses. What leaders need today is help to make better use of the tools they already have. That is what we do at Outlier: we improve the relationship between people and their data.We believe that success in life and success in business are not separate things, but intertwined as part of our lives. It is important to us that the journey we take with our company is as positive as the destination we hope to reach.
- Series B
- 6.6k employees
- Founded 2015

6
Shipt· Birmingham, Alabama, United States
Through a community of shoppers and a convenient app, Shipt provides personal shopping and delivery and is available to 80% of households in more than 5,000 U.S. cities. Shoppers go above and beyond, communicating in real time about preferences and substitutions. A curated marketplace of retailers, Shipt offers access to a variety of stores and product categories including fresh foods, household essentials, wellness products, office and pet supplies. Shipt is an independently operated, wholly owned subsidiary of Target Corp. Founded and headquartered in Birmingham, Alabama, Shipt also maintains an office in San Francisco. For more information, visit Shipt.com.
- Series B
- 6.5k employees
- Founded 2014
7
Driver· San Francisco, California, United States
Based in San Francisco and Shanghai, Driver is a technology platform that connects cancer patients to treatments and knowledge, all over the world, to get more life. With an app for the patient and an app for the doctor, Driver’s platform enables any cancer patient, regardless of their location, to access treatment options across Driver’s global network of cancer centers without leaving home. Driver’s network includes over 30 of the world’s leading cancer centers, including its founding members the US National Cancer Institute and the Chinese National Cancer Center. Other members of Driver’s network include the Cleveland Clinic, Mayo Clinic, Massachusetts General Hospital, University of California San Francisco, University of California Los Angeles, Duke, University of North Carolina, and Emory. Driver was founded in 2015 by two physicians, Dr. William R. Polkinghorn and Dr. Petros Giannikopoulos, and Driver’s lead investor is Horizons Ventures (Li Ka Shing).
- Series B
- 6.5k employees
- Founded 2015
8
WhatsApp· Menlo Park, California, United States
WhatsApp is a fast, simple and reliable way to talk to anyone in the world. More than 1.5 billion people across 180+ countries use WhatsApp to stay in touch with friends and family, anytime and anywhere. WhatsApp is not only free but also available on multiple mobile devices and in low connectivity areas — making it accessible and reliable wherever you are. It's a simple and secure way to share your favorite moments, send important information or catch up with a friend. WhatsApp helps people connect and share no matter where they are in the world.For many people in the world WhatsApp is a lifeline. We're looking for engineers, designers, researchers, product managers, technical program managers, customer ops, consumer marketing, and more. Come join our teams and make impact at scale.
- Series B
- 5.7k employees
- Founded 2009
9
Tredence Inc.· San Jose, California, United States
Tredence is a global data science solutions provider focused on solving the last mile problem in AI. The 'last mile' is the gap between insight creation and value realization. Headquartered in San Jose, the company embraces a vertical-first approach and an outcome-driven mindset to help clients win and accelerate value realization from their analytics investments. Tredence is a Great Place to Work-Certified and a 'Leader' in the Forrester Wave: Customer Analytics Services. Tredence is 3500+ employees strong with offices in San Jose, Foster City, Chicago, London, Toronto, Delhi, Chennai and Bangalore, with the largest companies in retail, CPG, hi-tech, telecom, healthcare, travel, and industrials as clients.In April 2025, we welcomed Further Advisory, a banking and financial services consulting specialist, into the Tredence family. Their sector-deep strategy expertise combined with our AI-driven decision-intelligence platform now helps global BFSI clients modernize faster, manage risk smarter, and unlock new growth at scale.
- Series B
- 4.6k employees
- Founded 2013
10
Sama· San Francisco, California, United States
What Does Sama DoSama gets your AI project to production—and helps you stay there.Sama is chosen by high-performing GenAI and CV teams across the full AIdevelopment lifecycle, combining expert services with reliable execution thatscales—delivering results, dependable datasets, and continuity even as things change.Our services cover the full AI lifecycle:● Data Strategy & Consulting – Aligning data needs to model goals, definingquality standards, and setting the foundation for faster, more confidentdevelopment● Annotation & Labeling – Using full-time, domain-trained teams with built-in QA to deliver precise, production-ready training data.○ Annotation Workflows: Validation, Classification, Tagging, Enrichment○ GenAI Workflows: Prompt Engineering, RAG embedding, Retrieval-AugmentedGeneration (RAG), Content Moderation & Filtering...● Model Evaluation – Scoring, ranking, and validating model outputs throughstructured, rubric-based evaluation and human-in-the-loop reviewWe don’t just deliver data—we embed in your workflows. Our dedicated teams,integrated QA, and platform support accelerate time-to-quality and give you the control and flexibility needed to iterate with speed and confidence.
- Series B
- 4.3k employees
- Founded 2008

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Find engineers at Series B companies in the United States

Series B companies in the United States are some of the fastest-moving employers in the market. The list above ranks the largest Series B-stage companies headquartered in the United States by current headcount, drawn from public LinkedIn and Crunchbase records. With 3,702 matching companies in Refolk’s index, the density of senior engineers, designers, and founders is unusually high.

At Series B, teams tend to be small, ambitious, and on the hunt for senior talent. The companies on this list are good signals for where the the United States talent market is heating up - and for which engineers and founders are about to become tomorrow’s operators.

Refolk converts this list into a live search. Ask for “founders of Series B companies in the United States” or “senior engineers at Series B companies in the United States hiring” and Refolk returns a ranked shortlist with evidence behind each match.

How this list is built

Refolk pulled Series B companies headquartered in the United States from public LinkedIn and Crunchbase records, ranked them by current employee count, and kept those with at least 5 employees. The list refreshes once a day.

Last refreshed: Wed, 05 Aug 2026 11:33:49 GMT

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How is this ranking built?

The list draws on the public company graph - headcount and growth signals, funding history, and recency. The criteria chips at the top show exactly which filters produced it, and the methodology section explains the ranking.

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The underlying index updates continuously and this page re-renders at least daily. Last refreshed: Wed, 05 Aug 2026 11:33:49 GMT.

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