Section 106 Explained for Archaeologists

Section 106 is the part of US historic preservation law that creates more archaeology work than any other. If you work in cultural resource management (CRM), or want to, you will hear about it constantly. This guide explains what it is, the terms you need, and how the review process works under the current regulations.

What Section 106 is

Section 106 of the National Historic Preservation Act of 1966 requires federal agencies to consider the effects on historic properties of projects they carry out, assist, fund, permit, license or approve. The review gives the Advisory Council on Historic Preservation (ACHP), other interested parties and the public a chance to weigh in before the agency makes its final decision.

The law sets a review process, and the ACHP's regulations at 36 CFR Part 800 spell out how that process works. This guide describes those regulations as they stand today.

Why it matters for archaeologists

When a project needs federal money, a federal permit or a federal approval, Section 106 usually applies. That covers a great deal of construction: highways, pipelines, transmission lines, solar and wind projects, reservoirs, and development on federal land. Agencies and the companies that apply to them often hire archaeologists to find and evaluate historic properties, so a large share of private-sector archaeology exists because of Section 106.

Federal agencies also employ their own archaeologists to manage compliance, and you can see those openings on our federal archaeology jobs page. Other laws can apply at the same time, including state environmental review laws and, where human remains or certain cultural items are involved, the Native American Graves Protection and Repatriation Act.

Key terms

The regulations define the terms you will use every day. In summary:

Undertaking: a project, activity or program funded in whole or in part under the direct or indirect jurisdiction of a federal agency. That includes projects carried out by or on behalf of an agency, projects carried out with federal financial assistance, and projects that need a federal permit, license or approval (36 CFR 800.16(y)).
Historic property: any prehistoric or historic district, site, building, structure or object included in, or eligible for inclusion in, the National Register of Historic Places. It includes related artifacts, records and remains located within the property, and properties of traditional religious and cultural importance to an Indian tribe or Native Hawaiian organization that meet the National Register criteria (36 CFR 800.16(l)).
Area of potential effects (APE): the geographic area within which an undertaking may directly or indirectly cause changes in the character or use of historic properties, if any exist. It depends on the scale and nature of the undertaking and can differ for different kinds of effects (36 CFR 800.16(d)).
SHPO and THPO: the State Historic Preservation Officer administers the state's historic preservation program. A Tribal Historic Preservation Officer has taken on the SHPO's responsibilities for Section 106 on tribal lands.

How a property becomes "eligible"

Historic properties are properties listed in, or eligible for, the National Register. The National Register criteria (36 CFR 60.4) look for properties in districts, sites, buildings, structures and objects that:

Criterion A: are associated with events that made a significant contribution to the broad patterns of our history.
Criterion B: are associated with the lives of persons significant in our past.
Criterion C: embody the distinctive characteristics of a type, period or method of construction, represent the work of a master, possess high artistic values, or represent a significant and distinguishable entity whose components may lack individual distinction.
Criterion D: have yielded, or may be likely to yield, information important in prehistory or history.

Archaeological sites are very often evaluated under Criterion D, which asks about their information potential. The regulations also say that, ordinarily, properties that have achieved significance within the past 50 years are not considered eligible, with limited exceptions.

The four steps

The current regulations organize the review into four steps.

1. Initiate the process

The agency decides whether the action is an undertaking and whether it is the kind of activity that could affect historic properties. If it has no potential to cause effects, the agency has no further obligations under Section 106 (36 CFR 800.3). Otherwise it identifies and involves the State or Tribal Historic Preservation Officer, Indian tribes and Native Hawaiian organizations, local governments and applicants entitled to take part, and others with a demonstrated interest, and it plans how the public will be involved. Many steps in the process give the SHPO or THPO 30 days to respond.

2. Identify historic properties

The agency determines and documents the area of potential effects and makes a "reasonable and good faith effort" to identify historic properties within it (36 CFR 800.4). That effort typically includes background research, consultation and field investigation such as survey. Properties are then evaluated against the National Register criteria. The result is one of two findings: no historic properties affected, or historic properties affected.

3. Assess adverse effects

If historic properties may be affected, the agency applies the criteria of adverse effect. An adverse effect is found when an undertaking may alter, directly or indirectly, any of the characteristics that qualify a property for the National Register in a way that would diminish the property's integrity (36 CFR 800.5). The agency can propose a finding of no adverse effect, and consulting parties have 30 days to review it. If an adverse effect is found, the agency consults further to resolve it.

4. Resolve adverse effects

The agency consults with the SHPO or THPO and other consulting parties to explore ways to avoid, minimize or mitigate the adverse effects (36 CFR 800.6). The result is often written up in an agreement document.

Where fieldwork fits

Archaeologists do much of the work in steps 2 and 4. Identification usually involves background research and field survey. When a site may be eligible, testing helps to evaluate it. When an adverse effect cannot be avoided, mitigation may include data recovery excavation. Many states and agencies use the terms Phase I, Phase II and Phase III for these stages, but the names and definitions vary, so follow the guidelines in the state where you work.

Field technicians carry out most of the survey and excavation. Principal investigators are responsible for the quality of the technical reports that go to the agency and to the SHPO or THPO. See archaeology field technician jobs and principal investigator jobs.

Who may do the work

The National Historic Preservation Act requires each federal agency responsible for the protection of historic resources, including archeological resources, to ensure that actions taken by its employees or contractors meet professional standards under regulations developed by the Secretary of the Interior (36 CFR 800.2(a)(1)). That is why job postings and contracts so often ask for archaeologists who meet the Secretary of the Interior's Professional Qualification Standards. Our guide to the standards and the RPA explains them.

Consultation with tribes

Federal agencies have a responsibility to consult. They must make a good-faith effort to identify Indian tribes and Native Hawaiian organizations that may attach religious and cultural significance to historic properties in the area of potential effects, and they must include those that ask in writing to take part. Archaeologists support this process by providing accurate information and by respecting what tribes choose to share.

What may change

The ACHP announced on July 24, 2026 that its members voted to advance a proposed rule revising the Section 106 regulations. Before it can be published, the draft goes through interagency review. Law firms and advocacy groups have published summaries of the draft, but the proposal is not final and its details may change, so we do not summarize them here. Because the rules may change, check the ACHP website and the Federal Register before relying on any detail in this guide, and read the proposed rule itself once it is published.

Sources and further reading

This guide is general information, not legal or professional advice. Regulations, standards and employer practices change, so check the official sources linked above before relying on any detail.